Under this heading I shall treat in turn Marc-Wogau's discussion of the following topics.

  1. Particular Individuals,
  2. Identity and Difference,
  3. Existence, and
  4. Material Things.
(The order in which I take them is not in all cases the same as that in which they occur in Marc-Wogau's book.)

(A) Particular Individuals.

       Marc-Wogau's discussion of this topic is to be found in chapter III, which is entitled On Individual and Universal Objects. I must confess that I do not find it easy to follow, and it is quite likely that I have only imperfectly understood it.

       One thing at least is certain. Marc-Wogau holds that the notion of a particular individual presupposes the notion of what he calls a 'Bestimmungs komplex'. This has to be distinguished from what he calls a 'Bestimmung', whether compound or noncompound. We must now try to grasp these notions by means of Marc-Wogau's statements and illustrations.

       We are told, on the top of page 156, that the word 'Bestimmung' is used in the book in a wider and a narrower sense. In its wider sense it means 'anything that can be predicated in any sense of any object'; so it can presumably be translated by 'predicate'. When it is used in this sense Marc-Wogau says that 'certain Bestimmungskomplexe are also Bestimmungen'. So it appears that some (though presumably not all) Bestimmungskomplexe are predicates. But in the present context the word 'Bestimmung' is used in a narrower sense. As regards this we are told (i) that no Bestimmungskomplex is a Bestimmung in this sense, and (ii) that every Bestimmung in this sense is a 'determinable or determinate'. It is not asserted that every determinable or determinate is a Bestimmung in this sense; but this is not denied, and I suspect that it is intended.

      Examples of Bestimmungen in the narrower sense are 'red', 'triangular', and 'equilaterally triangular'. It seems to me that what is common and peculiar to all of them is that each is a certain relatively determinate form of a certain relatively indeterminate predicate. Thus, to be red is to be coloured in a certain way; to be triangular is to be shaped in a certain way; and to be equilaterally triangular is to be triangular in a certain way. If so, we may perhaps translate 'Bestimmung', in the narrower sense, by the phrase 'specified generic predicate'.

      Marc-Wogau points out that there are two different kinds of specified generic predicate. 'Red' is an example of the one, and both 'triangular' and 'equilaterally triangular' are examples of the other. The difference may be put as follows. 'To be red' is simply to be coloured redly. One cannot express the differentia between the specific predicate 'red' and the generic predicate 'coloured' except by repeating the word 'red' (or some linguistic equivalent of it) in an adverbial form. But 'to be triangular' is to be a rectilinear plane figure with three sides, and 'to be equilaterally triangular' is to be triangular with equal sides. Here the differentia can be analysed and expressed in independent terms. We could make a person understand what it is to be triangular, even though he had never seen an instance of triangularity, provided that he understood what it is to be a rectilinear plane figure and was acquainted with the notion of cardinal numbers in general and the number three in particular. Marc-Wogau calls specified generic predicates of the former kind 'non-compound' (einfach), and those of the latter kind 'compound' (zusammengesetzt). He points out that a predicate which is non-compound in this technical sense may yet be 'complex' (komplex) in another sense. Anything that is red, e.g., has redness of a certain shade, a certain intensity, and a certain saturation. I propose to call such factors as these 'dimensions of comparability'. (In the case of sound, e.g., the dimensions of comparability are pitch, loudness, and tone-quality.) Thus we may state Marc-Wogau's doctrine here by saying that a specified generic predicate which is non-compound, in the sense that its differentia cannot be analysed and expressed in independent terms, may yet be complex, in the sense that it has several dimensions of comparability.

      We come now to Bestimmungskomplexe. The predicate of 'being a red triangle' is given as an example. If we compare this with the predicate 'equilaterally triangular' or 'intensely red', we see that the difference may be put as follows. To be equilaterally triangular is to be triangulat in a certain way; and the same is true mutatis mutandis of being intensely red. But it would be nonsensical to describe an object which was red and triangular as either 'redly triangular' or 'triangularly red'. It is redly coloured and triangularly shaped. The connexion between the two relatively indeterminate predicates of 'being coloured' and 'being shaped', and the consequent connexion between the relatively determinate form of the one and the relatively determinate form of the other (e.g., between being redly coloured and being triangularly shaped) which happen to belong to the same object, is something unique and peculiar. It is obviously completely different from the connexion between a relatively indeterminate predicate and the relatively determinate form of it which happens to belong to a certain object, e.g., between the predicate of being triangular and that of being equilaterally triangular in the case of an object which happens to be an equilateral triangle. I propose to call it 'compresence'. It must be understood that this phrase is not intended to imply or to exclude any particular theory about substance and attributes.

      I have stated all this in my own way, but I think that it agrees with what Marc-Wogau has in mind. I will now add the following remarks. In the case of a Bestimmungskomplex we are concerned with what might be called 'relatively contingent compresence'. It is, perhaps, necessary that anything which has colour should have shape, and that anything which has shape should have colour. On that question I do not wish to express a decided opinion here. But, if a certain thing is, e.g., red and triangular, its redness and its triangularity are contingent to each other. It might have been red and had any other shape, and it might have been triangular and had any other colour.

      Marc-Wogau points out that such a complex predicate as 'red-and-hard-and-circular' is the most elementary kind of Bestimmungscomplex. Consider the case of an object which might be described as a circular area with one half red and the other half green. The predicate here is also an example of a Bestimmungskomplex. Plainly the predicates 'red' and 'green' are contained in it in a different way from that in which the predicates 'red', 'hard' and 'circular' are contained in the Bestimmungskomplex 'red-and-hard-and-circular'. So we must recognize that a Bestimmungskomplex may have a very elaborate internal structure.

      Marc-Wogau says that certain predicates can, and others cannot, be combined into a Bestimmungskomplex. He says that this is an ultimate fact. The examples which he gives to illustrate this alleged fact are the following. 'Red' and 'triangle' can be so combined; 'red' and 'hard' cannot; but 'red' and 'hard' and 'surface' can.

      I suppose that the ground for his statements is the following. It is grammatically correct to describe an object as 'a red triangle' or as 'a red hard surface'; but it is not grammatically correct to talk of a 'red hard' or a 'hard red'. It seems to me that there is nothing substantial in this distinction, and that it depends simply on a contingent peculiarity of the English and the German languages. We happen to have a substantive-word 'triangle' for surfaces whose shape is triangular, but no substantive-word for surfaces whose texture is hard or surfaces whose colour is red. Suppose that we could talk of 'a red' or 'a hard', as we can talk of 'a triangle'. Then we could talk of 'a triangular red' as well as of 'a red triangle'. And we could talk of 'a red hard' or 'a hard red'. In all these cases the predicate can be expressed by such phrases as 'red-and-triangular' or 'red-and-hard'; and then all appearance of the alleged difference vanishes. In both cases it is presupposed that the object is, or has, a surface; for each of the predicates 'red' and 'triangular' and 'hard' is a specific modification of a generic characteristic which can belong only to extended objects.

      We come next to the case of common nouns, e.g., 'book' or 'penny', used as predicates, e.g., in such phrases as 'That is a book' or 'There is a penny on the table'. Marc-Wogau holds that these express a certain special sub-class of Bestimmungskomplexe. I take it that what he means is this. By describing an object as 'a book' or 'a penny' we are ascribing to it a complex predicate composed of relatively contingent compresent simpler predicates; although these simpler predicates are not explicitly named, as when we describe an object as a 'red hard triangle'. A common noun, used predicatively, may be said to express an implicit Bestimmungskomplex.

      Finally we come to the objects denoted by such phrases as 'This X', where 'X' is either an explicit Bestimmungskomplex-phrase, e.g., 'red hard triangle', or an implicit Bestimmungskomplex-phrase, e.g., 'book' or 'penny'. According to Marc-Wogau, any such phrase denotes a Bestimmungskomplex of the following peculiar kind. Among its constituents are included a local and a temporal predicate, and these are completely determinate. If I understand him aright, the phrase 'This red hard triangle', e.g., denotes what might be otherwise expressed by the phrase 'Redness, hardness, and triangularity compresent here now'. And I suppose that the phrase ' this penny ' would denote what might be otherwise expressed by the phrase 'Such and such predicates quiz., those which constitute a definition or description of a penny) compresent here now'.

      There are two explanatory comments to be noted here. (i) It is admitted that one might look at a certain object and say of it correctly and truly: 'That table was in my grandfather's house. I inherited it. It has been away to be polished and has lately come back'. For an account of Marc-Wogau's complete treatment of this the reader must wait until he comes to Sub-Section D of the present Section of this paper, where I deal with the concept of Material Thing. It must suffice for the present to say that, according to Marc-Wogau, the primary sense of 'This table' is that in which it applies to a Bestimmungskomplex in which the local and the temporal predicate-constituents are both completely determinate. The sense in which it applies to the table as an enduring continuant with a variegated history is derivative from this.

       (ii) According to Marc-Wogau, it is only the local and the temporal predicate which must be completely determinate when such a phrase as 'This table' is used in the primary sense. The other predicates which are either explicit or implicit constituents of such a Bestimmungskomplex may be, and generally are, incompletely determinate.

      Now Marc-Wogau identifies a Particular Individual with a Bestimmungskomplex of the kind just described, i.e., with one which contains as constituents a perfectly determinate local and temporal predicate and as other constituents other kinds of predicate which need not be completely determinate.

      He proceeds to compare this account of particulars with others that have been given by eminent philosophers, e.g., Russell, Stout, and Johnson. I do not propose to consider these comparisons in detail; but it will be worth while to notice certain statements which occur in them, because they throw light on Marc-Wogau's own theory.

      (i) It has been said that universals and particulars may be distinguished by the fact that universals have instances, whilst particulars are instances of universals but do not have instances. Marc-Wogau rightly says that, if we are to make use of this, we must clear up the notion of 'instance'. He then embarks on a long and difficult discussion which occupies pages 170 and 171 of his book.

      It seems to me that this discussion would be greatly simplified if one began by pointing out that the word 'instance' is used in the following two senses.

  1. It would be in accordance with usage to say: 'Scarlet is an instance of red' or 'An oak is an instance of a tree'. In this sense 'instance of' means 'determinate under' or 'species of'.
  2. It would also be in accordance with usage to remark, on seeing a red flash or pointing to a tree, 'That is an instance of red' or 'That is an instance of a tree', as the case might be. Here 'instance of' means 'determinately dated and localized occurrence of'. A universal has instances, in the sense of sub-species or determinates under it, unless it happens to be completely determinate. It has, or may have, instances, in the sense of determinately dated and localised occurrences, whether it is or is not completely determinate.

     Now it is true that a determinately localised and dated occurrence of scarlet, e.g., is ipso facto a determinately localized and dated occurrence of red, just because scarlet is a determinate under red. It is also true that each is a particular. But it does not follow that a particular can have instances in either of the two senses in which a universal can do so. Scarlet-here-now is not an instance of red-here-now, either in the sense in which scarlet is an instance of red, or in the sense in which scarlet-here-now is an instance both of scarlet and of red. For scarlet-here-now is not a species of red-here-now; it is not a species of, or determinate under, anything. And it is not a determinately localised and dated occurrence of red-here-now; it is such an occurrence of scarlet and equally of red. I think it is plain, then, that Marc-Wogau is right in saying that, on his view of particulars, a particular would not have instances in either of the two senses in which a universal may have instances.

      (ii) In comparing his view with the doctrine, asserted by both Johnson and Russell, that a distinguishing mark of a particular is that it can function in a proposition only as a logical subject, Marc-Wogau makes the following remark. There is, he says, a fundamental question which can be raised about both these philosophers. Do they regard a logical subject as (a) a complex whole in which its predicates can be distinguished as constituent factors, or (b) something which remains over when one abstracts from all its predicates? He says that, on the first alternative, their view need not be (though of course it might be) fundamentally different from his own, according to which a particular is a Bestimmungskomplex containing a completely determinate local and temporal predicate. On the second alternative, he says, there would be a radical difference.

      Now it seems to me that Marc-Wogau has not distinguished enough alternatives here. I should have thought that at least the following three need to be distinguished.

  1. That a particular is a complex whole whose only elements are its predicates.
  2. That it is a complex whole which contains its predicates as elements, but also contains an element of an entirely different kind from any predicate.
  3. That, whether it be complex or not, it does not contain any of its predicates as elements.
I take it that Marc-Wogau's theory is a form of Alternative 1. A person who accepted Alternative 2 might hold either
  1. that the non-predicative element in a particular could occur in isolation, or
  2. that it could not.
It should be noted that a person who held Alternative 2 would be very liable to use the word 'particular' or 'substance' ambiguously. He might use it sometimes to mean the complex whole composed of the predicates and the non-predicative element, and sometimes to mean the non-predicative element in such a whole. He would be specially liable to make this confusion if he held Alternative 2 in the Form b, i.e., if he thought that the non-predicative element in a particular cannot occur except in combination with predicates to form a particular. We might avoid this ambiguity by using the word 'hypostasis' for the alleged non-predicative element, and the word 'substance' or 'particular' for the complex whose elements are an hypostasis and a number of predicates.

     I take it that, on Marc-Wogau's view, a particular might be symbolized by some such formula as R(P1, P2 . . .; s, t). Here P1, P2, etc., represent predicates, other than those of local and temporal position, which may be relatively indeterminate. The letters s and t represent respectively a perfectly determinate spatial position and a perfectly determinate date. They are separated from P1, P2, etc., by a semi-colon to show that they perform a unique function in the complex, quite unlike that of the other predicates. The R outside the bracket represents a unique mode of relationship or form of union or 'bond' or 'tie', which I have called 'compresence'.

      Alternative 2 would be represented by some such formula as S(0; P1, P2 . . .; s, t). Here 0 represents the non-predicative element which I have called an 'hypostasis', and S represents a bond between factors of three different kinds, viz., the hypostasis, the non-spatio-temporal predicates, and the local and temporal positional predicates.

      (iii) It has been said that a particular is something which is completely determinate in every respect. Marc-Wogau has to consider how this is related to his doctrine that a particular is a Bestimmungskomplex in which only the local and temporal predicates need be completely determinate.

      Let us simplify the question at the outset, as Marc-Wogau does, by confining our attention to the case of a visual prehensum. It does seem to me that a visual prehensum must have a certain completely determinate colour, shape, extension, etc., as well as a certain completely determinate date and position in a certain visual field. In having these determinates it will, of course, ipso facto have all the less determinate predicates under which any of them fall. But it seems to me unintelligible to suggest that a determinable predicate could be manifested at a certain time and place without being there and then manifested in a certain perfectly determinate form. On the other hand, I have no difficulty in admitting that a prehended particular, e.g., a visual prehensum, may be, and perhaps always is, prehended as having characteristics which are not completely determinate. One could say that it is 'circular or nearly so', 'scarlet of a light shade and considerable intensity' and so on; but one could not go further than this. (In the case of colours and of most shapes we have no names for perfectly determinate forms. So, even if one prehended a particular as having a certain perfectly determinate colour and shape, one could not express in words anything more than a certain relatively indeterminate colour and shape under which these determinates fall.)

      Before concluding this sub-section I will make some general remarks about the theory of particulars of which I take MarcWogau's theory to be an instance.

      (1) It has its maximum plausibility when confined to visual prehensa. It is not unplausible to hold that, when we say that a scarlet visual prehensum exists, we mean simply that scarlet is now being manifested in a certain position in a certain visual field. But even in this case the expression 'scarlet-here-now', which is often given as the right translation, is terribly inadequate. 'Here', e.g., does not distinguish between one position in a visual field and other simultaneous positions in it. A scarlet and a blue visual prehensum, or for that matter two scarlet visual prehensa of precisely the same shade, shape, and size, may co-exist in the same visual field. Again, they may exist in different contemporary visual fields.

      (2) Then something must be said about the shape and extension of a visual prehensum. At the very least it must be described as a certain area in a certain position in a certain visual field pervaded by a certain colour during a certain period. When all this has been added one wonders whether the visual field is not being treated as a kind of hypostasis; a kind of Substantival Absolute Space waiting ready to be 'inhered in' here or there by this or that colour. Perhaps the answer that would be made is that, while 'inherence' in general is a vague unintelligible term, the notion of the pervasion of an area of a visual field by a colour is clear and intelligible.

      (3) The complication increases when we pass from particulars to which only one kind of predicate, e.g., colour, is ascribed to particulars which are described, e.g., as brown and cold and hard and round. What is the analysis of 'compresence' when these very different kinds of predicate are said to be compresent in a certain perfectly determinate position at a certain date? And what kind of space is it that houses these very different predicates?

      (4) So far we have spoken only of those predicates which are qualities, e.g., redness, coldness, etc. But a very important class of predicates in the case of a material thing or a person are its dispositional properties, e.g., its melting-point, its density, its electrical conductivity, and so on. Can the inherence of these in a particular be dealt with on the same lines as that of pure qualities, viz., by talking of 'compresence' in a certain position at a certain date? And, if so, will not the notion of compresence need to be modified still further?

(B) Identity and Difference.

      Marc-Wogau discusses this subject from page 90 to page 102. He begins by distinguishing three kinds of difference, which he calls numerical, qualitative, and abstractive.

      Numerical difference can be predicated when and only when we can properly speak of two or more objects.

      He gives three examples of qualitative difference.

  1. Two predicates can be said to be qualitatively different if they cannot both at the same time and in the same respect be applied to the same subject. 'Red all over' and 'blue all over' would thus be qualitatively different predicates.
  2. Two Bestimmungskomplexe may be qualitatively different. The examples given are 'red sphere', 'green sphere', and 'red cube'. Suppose we substitute for the phrase 'red sphere' the equivalent and mote explicit phrase 'redly coloured and spherically shaped surface', and make similar substitutions. mutatis mutandis, in the two other cases. Then it becomes plain that any two such Bestimmungskomplexe are qualitatively different if any determinable which is an element in both is present in different determinate forms in the two.
  3. More elaborate examples of qualitative difference between Bestimmungskomplexe are the following. 'Spot consisting of a white circle surrounded by a black ring' and 'Spot consisting of a black circle (of the same size as the white one) surrounded by a white ring (of the same size as the black one)'.

      Abstractive difference also covers several cases. It may apply either (1) to universals, or (2) to particulars. In the case of universals there are two possibilities.
(1.1) The example here is 'triangular' and 'equilaterally triangular', i.e., a relatively indeterminate predicate and the same predicate specified by a differentia.
(1.2) The example here is 'three-sided figure' and 'equal-sided figure'. Here we have the same relatively indeterminate predicate specified by two different differentiae which are not qualitatively different, because not incompatible with each other. (I can see that this is not an instance of qualitative difference, as defined by Marc-Wogau; but it is not clear to me that it is appropriate to call it an instance of 'abstractive' difference.,

      (2) The example which Marc-Wogau gives of abstractive difference as applied to particulars is important. Suppose that a cube is lying on a table with a certain face F6 downwards and a certain other face F3 upwards. It is observed from opposite sides of the table by two observers X and Y. X can see the faces F1, F2, and F3 and no others; Y can see the faces F3, F4, F5 and no others. It is assumed that the positions of the observers are such that what each prehends is prehended by him neither as distorted in shape nor foreshortened in size. Marc-Wogau says that the two prehend numerically different objects, but that these objects differ only abstractively. Each object has certain features which the other lacks; but there would be no inconsistency in supposing that all the features which belong to either were compresent in a single object.

      This example should be contrasted with the case of two observers who look at the same penny, one from a great distance and in a very oblique direction, and the other from a few feet away and in a direction which is exactly or nearly at right angles to its surface. Here also the two prehend numerically different objects, but now the objects differ qualitatively and not only abstractively. The one object is prehended as round and unforeshortened; the other as elliptical and 'unnaturally small'. It would be inconsistent to ascribe roundness and ellipticity of contour, or two different extensions, to a single object.

      It should be noted that Marc-Wogau insists that, when two contemporary particulars are said to differ only attractively, it us assumed that the determinate spatial position is the same in both of them. If one occupies a different position from the other, this constitutes ipso facto a qualitative difference between them.

      Lastly, Marc-Wogau asserts that either qualitative or abstractive difference entails numerical difference; but neither qualitative nor abstractive difference entails the other. (It would appear from the examples that qualitative difference in a given respect excludes abstractive difference in that respect. But neither excludes the other in a different respect.)

      If I am not mistaken, the notion of abstractive difference, as applied to particulars, can be illustrated as follows. Let P. Q . . . represent characteristics, which may be incompletely or completely determinate. Let p, q, . . . represent characteristics which are determinates under P, Q, . . . respectively when the latter are not completely determinate. Let s represent a perfectly determinate spatial position, and t a perfectly determinate date. Consider the following sets of Bestimmungskomplexe

  1. P-at-s-at-t and (P & Q)-at-s-at-t. E.g., brown-here-now and (brown-and-round)-here-now.
  2. (P & Q)-at-s-at-t and (Q & R)-at-s-at-t. (It is assumed here that there is no incompatibility between P & Q and R. and no incompatibility between Q & R and P.) E.g., (brown-and-round)-here-now and (round-and-cold)-here-now.
  3. (P & Q)-at-s-at-t, (p & Q)-at-s-at-t, (P & q)-at-s-at-t, and (p & q)-at-s-at-t. E.g., red-and-triangular)-here-now, (scarlet-and-triangular)-here-now, (red-and-equilaterally-triangular)-here-now, and (scarlet-and-equilaterally-triangular)-here-now.
In each of these three sets, according to Marc-Wogau, we have two or more particulars, which differ only abstracttuely.

      Now what seems to me odd is to assert with conviction that in all such cases there are two or more particulars. This is of course entailed by saying that abstractive difference involves numerical difference. It seems not unplausible to say that there are two particulars in the example of the objects visually prehended by the two observers of the cube. But it seems to me most paradoxical to say this, e.g., in the example of (red-and-triangular)-here-now and (scarlet-and-equilaterally-triangular)-here-now. Surely the ordinary way of formulating this situation would be to say that there is a single particular, which is less determinately described in the one case and more determinately described in the other. It is not clear to me that Marc-Wogau is logically obliged by his account of particulars to say that there are two or more particulars in all such cases. But, if that is a logical consequence, I should be inclined to regard it as a prima facie objection to his account of particulars.

      We can now pass to Marc-Wogau's account of 'one and the same', as applied to particulars where there is no question of difference of date. (The case of identity through time has to be considered separately.)

      (1) We may use the phrase to deny numerical difference. We may mean to assert, e.g., that, although there are two different descriptions, yet there is just one object answering to both. (As I have said, it seems to me that many cases which Marc-Wogau would count as instances of numerical difference with mere abstractive difference fall much more naturally under this head.)

      (2) We may intend to deny certain qualitative differences between two objects. I think that a good example of this would be when we call two simultaneous occurrences of the same written or spoken type-word 'the same word'. Certain likenesses between two tokens of the same type-word are so much more important than the unlikenesses, for everyone but the typographer or the phonologist, that we commonly ignore the latter.

      (3) We may intend to deny all qualitative difference, but not abstractive difference; and therefore, according to Marc-Wogau, not numerical difference. He says that the objects prehended by the several observers of the cube in the above example, and also the cube itself (assuming that their visual experiences are veridical and that they really are both seemg a certain cube), are 'one and the same object' in this sense.

      Of course all parties are agreed that, in thus example, there is a sense in which it is correct to say that both are 'seeing the same object', viz., a certain cube, and a sense in which it is correct to say that they are seeing partly different objects, viz., different parts of the surface of that cube. Marc-Wogau admits that it is possible to give a different account of this situation from that which he has given. E.g., it might be said that the different objects which the two observers visually prehend are alike in nature, but that they differ fundamentally in nature from the one cube which they both see. And it might be held that each of the former stands to the latter in a certain determinate form of the same peculiar relation, viz., that of being an aspect or appearance of it. That is the kind of account which most Sense-Datum Theorists would give. Marc-Wogau thinks that their reasons are inconclusive, and wishes to substitute the account given in Sub-section B of the Introduction of this paper.

      (4) Two objects may be called 'one and the same' when we do not mean to deny even qualitative difference between them. Take, e.g., the example of the two persons looking at a penny lying on the table. The objects prehended respectively by the near-by observer who looks straight downwards on the penny and the distant observer who views it obliquely differ qualitatively and therefore numerically. But the two observers would be said to be seeing 'the same part of the same penny'.

      It seems to me that all that Marc-Wogau is really entitled to say at this stage of the discussion is the following. We certainly have two different descriptions, viz., 'the object visually prehended by A' and 'the object visually prehended by B'. Let us abbreviate these to 'A's visual prehensum' and 'B's visual prehensum'. The following propositions are certainly true.

  1. A prehends his prehensum as round.
  2. B prehends his prehensum as elliptical.
  3. One and the same object cannot at the same time have a round and an elliptical contour.
Now, if and only if it is assumed that a visual prehensum must have any quality which it is prehended as having, it follows that A's visual prehensum differs qualitatively from B's. And in that case it follows that the two descriptions 'A's visual prehensum' and 'B's visual prehensum' describe two different objects, i.e., that we have a case of numerical difference.

      But, unless this assumption is made (and Marc-Wogau discusses it elaborately elsewhere and seems inclined in a certain sense to reject it), there is no certainty that we have a case of qualitative and numerical difference here. Why not say that there is literally one particular, visually prehended by both A and B; but that at least one of these observes visually prehends it as having a characteristic which is other than and incompatible with a characteristic which it actually has?

      Be that as it may; Marc-Wogau thinks that this is a clear case of two qualitatively different objects being called 'one and the same'. He thinks that the phrase 'one and the same', when used in this sense, has no conventional connotation. The most that we can do is to mention certain conditions, one or more of which is generally fulfilled when the phrase is felt to be appropriate. He thinks that the most important of these are qualitative likeness, identity of position, and a common causal ancestor. But he says that any one of them may fail and yet the phrase 'one and the same' may be applied, and that any of them may hold and yet the phrase be withheld. He gives various examples to illustrate this.

      He points out that cases occur where two of these conditions are fulfilled but there is something which positively conflicts with the remaining one. Examples are the two objects visually prehended when one 'sees double'; the two objects prehended by different observers of the same 'ambiguous figure', to whom it appears in characteristically different ways; and so on. In such cases common-sense is uncertain whether to affirm or to deny 'sameness'.

(C) Existence.

      Marc-Wogau discusses the notion of Existence from page 67 to page 85. After a long discussion he distinguishes three senses in which 'existent' or 'non-existent' or some equivalent pair of opposites can be applied to particulars.

      (1) In the widest sense one says of any prehensum that it 'exists' so long as it is being prehended. This is regardless of whether it is prehended in a dream or hallucination or illusion or in normal waking perception. Marc-Wogau denotes this sense of 'exist' by E1.

      (2) Among objects which E1 we distinguish those which are prehended in normal waking perception from those which are prehended in dreams, delirium, or hallucinatory waking perception. The former are said to 'exist' or to be 'real'; the latter to be 'non-existent' or 'unreal'. The former would include both the visual prehensum of the person who sees the penny as round and of normal size, and that of the person who sees it as elliptical and foreshortened. This sense is denoted by E2.

      (3) If a prehensum E2 its prehended characteristics may differ either (i) only abstractively, or (ii) qualitatively, from the characteristics of the actual visum. In the former case we say that it 'exists in the strict sense'. The visual prehensum of the near-by observer who looks straight down on the penny exists in this sense; that of the other observer does not. This sense is denoted by E3.

      Marc-Wogau remarks that E1, E2, and E3 may not be three different meanings of the word 'exist'. It may be that the word, in each of its applications, has no conventional connotation; and that all that can be done is to describe in each case the conditions under which it would commonly be applied or withheld. The conditions for applying E1 are simple. It is applied at any time to all those objects and only those which are then being prehended. E2 is applied when and only when it is believed that an important factor in causing the visual experience was either the actual visum or some other material object connected with the latter in certain determinate ways. (I suppose that the latter alternative is intended to cover the case of such objects as mirror-images, double-images, etc.)

      The conditions under which E3 is applied are much more complicated. Marc-Wogau enumerates the following, without claiming that his list is exhaustive. (i) Congruence between sight and touch. (ii) Constancy of the visual appearances obtained under certain conditions (e.g., normal illumination) in spite of variations in other conditions. He admits that there are many exceptions and qualifications to be made here. I should have thought that appropriate variation of the appearances concomitantly with certain variations in the conditions was an equally important criterion for E3. (iii) Certain causal relationships to other objects already believed to E3.

      Marc-Wogau raises here the following logical question. Suppose that one could enumerate a rather large number of conditions C1, C2 . . . Cn, such that if any of them were believed to be present we should apply 'E3' and if all of them were believed to be absent we should refuse to apply it. Could we then say that 'E3' has a meaning, and that its meaning is the alternative characteristic C1-or-C2-or . . . Cn? Marc-Wogau thinks not. He holds that we should say that ' E3' has a meaning only if we thought that there is either a single non-alternative characteristic C or a conjunction of such characteristics C1 and C2 and . . . Cn, such that 'E3' is correctly applied when and only when C is believed to be present or C1 & C2 & . . . Cn is believed to be present, as the case may be.

      Now he thinks it most unlikely that there should be any quality or set of qualities answering to these conditions. But might there not be a relational property or a set of them, answering to these conditions, which would constitute the meaning of 'E3'?

      He finds the following difficulty in this suggestion. On this supposition what is meant by ascribing E3 to an object O is either

(i) that O stands in certain relations to certain other objects taken severally, or
(ii) that it stands in certain relations to a certain set of interconnected objects taken collectively.

Now he thinks that it would always be necessary to add the proviso that each of these objects, or this system of interconnected objects, as the case may be, exists. If 'exists' here means the same as 'E3', we have a logical circle in the attempted definition of 'E3'; if it does not, we have a fourth sense of 'existence' on our hands. (This does not seem to me to be certain. Might not the sense required be E1 or E2? Would not a Berkeleian or a Phenomenalist, e.g., say that it was E1?)

      On the whole Marc-Wogau is inclined to think that 'E3' is a label which is 'meaningless' in the following sense, viz., that there is no set of non-alternative characteristics such that it would be appropriate to apply it if and only if all of them were believed to be present. This label is commonly tacked on to a prehensum when any one, or any selection, of a number of alternative but not mutually exclusive conditions is believed to be fulfilled. He compares this to the process of marking certain material things with a cross in order to distinguish them from others. (There are generally reasons for this in any particular case. E.g., a frequent reason is that the things belong to a single person or that they are to be sent to a certain place.) When certain things have been so labelled they ipso facto acquire a common and peculiar property, viz., that of being marked with a cross. Similarly, when certain prehensa have, for one reason. or another, had the adjective 'E3' attached to them, they ipso facto acquire the common and peculiar property of being said to 'E3'. But this cannot be described as the meaning of 'E3', in the sense in which, e.g., the meaning of 'circle' is line all of whose points are equidistant from a fixed point.

(D) Material Things.

      Under this head Marc-Wogau discusses two general problems, viz.,

  1. (1) the Self-Identity of a thing through time, and
  2. (2) the Unity of a thing in relation to its many contemporary aspects.

(1) Self-identity through Time.

      The discussion of this problem occupies pages 2 to 16 of Marc-Wogau's book. I think that the following is the best way to introduce it. We have two definite descriptions, referring to two different moments of time, e.g.,

(i) 'The material object which occupied a certain place five minutes ago' and
(ii) 'The material object which occupies a certain place (it may be the same or a different one) now'.

Sometimes we say or imply that these are just two descriptions of a single object. E.g., 'the thing that was in the middle of my writing-table five minutes ago is in my hand now'. Sometimes we say or imply that each is a description of a different object. Under what conditions do we say that there is a single object answering to two such descriptions?

      Let us state the question in the following form. Under what conditions do we say that there is a single thing answering to two such descriptions as 'The material object which occupies s1 at t1' and 'The material object which occupies s2 at t2', where s1 and s2 may be either the same or different, but t1 and t2 are assumed to be different?

      I think it is plain that there would be a number of different cases to be considered if the question were to be treated fully. We may say that a material thing has remained at rest at s1 throughout the interval from t1 to t2 or that it has moved. If it has moved, it may have moved continually throughout the interval or it may have stopped from time to time. In either case it may have occupied any one position only once or it may have occupied one or more positions several times. (Several of these possibilities are illustrated by the case of a swinging pendulum.) Marc-Wogau, quite reasonably, refrains from mentioning these tiresome complications of detail. We will confine ourselves to the following two cases. (i) Where a material object is said to have remained at rest at s1 from t1 to t2. (ii) Where it is said to have moved continually and without occupying any position more than once from s1 at t1 to s2 at t2.

      If the question is formulated in this way, I think that MarcWogau's answers for the two cases would be as follows.

Case I.

      Here one would be inclined to say that there is a single thing answering to the two descriptions 'The material object which occupies s1 at t1' and 'The material object which occupies s1 at t2' if one believed (rightly or wrongly) that the following conditions were fulfilled.

  1. That for every moment t between t1 and t2 there is a particular answering to the description 'The material object which occupies s1 at t.
  2. That all such particulars are exactly or predominantly alike in their qualities.
  3. That, if there are differences of quality, it is true on the whole (though there may be occasional exceptions) that particulars of this set which are nearer to each other in time are more alike than those which are further apart in time

Case II.

      Here one would be inclined to say that there is a single thing answering to the two descriptions 'The material object which occupies s1 at t1' and 'The material object which occupies s2 at t2' if one believed (rightly or wrongly) that the following conditions were fulfilled.

  1. That for every moment t between t1 and t2 there is a particular answering to the description 'The material object which occupies s at t', where
    1. for each value of t there is a different value of s, and
    2. the values of s corresponding to any two values of t differ by an amount which tends to zero as the difference between the values of t tends to zero.
(ii) and (iii) are the same respectively as (ii) and (iii) in Case I.

      The following points should be noticed about these answers.

      (i) What is relevant is what the person who asserts or denies identity through time believes to be the case, not what really is the case if that should differ from what he believes.

      (ii) It is plain that, in accordance with Marc-Wogau's general account of particulars, we are concerned with a series of numerically different particulars, even when we correctly and truly talk of 'the same material thing'. For, according to that account, two descriptions of a particular, into which there enter different moments of time, are inevitably descriptions of different particulars.

      (iii) It will be noticed that, in stating the theory, I have talked throughout of 'the material object which occupies s at t' and not of 'the particular which occupies s at t'. I have done this deliberately for two reasons. In the first place, if I have understood Marc-Wogau's theory of particulars aright, there could be a plurality of particulars occupying the same place at the same time. If so, there would be nothing answering to the description 'the particular which occupies s at t'; for that implies that there is only one. Secondly, I understand Marc-Wogau to hold that it is impossible to describe the difference between a series of particulars which does, and one which does not, constitute a material thing without bringing in the notion of 'material thing'. I understand him to assert that all attempts to do this by means of the intrinsic peculiarities of the former kind of series are either inadequate or circular.

      Marc-Wogau lays considerable stress on the following feature of his theory. Although he has mentioned several conditions under which a person would be inclined to say that two descriptions, involving different moments of time, both apply to 'the same thing', he does not wish to assert that these conditions constitute the meaning of the phrase 'same thing at two different moments'. So far as I can understand, he is inclined to deny that this phrase has a meaning, in the sense in which, e.g., the word 'circle' has. In this view he associates himself with the Uppsala philosopher Phalen. This may be compared with the doctrine, already mentioned, that 'existence in sense E3' has no meaning but should rather be compared to a label.

      If I may state what I suppose to be Marc-Wogau's view on this point in my own way, I think that it comes to the following. Suppose that m1 answers to the description 'the material thing which occupies s1 at t1' and that m2 answers to the description 'the material thing which occupies s2 at t2'. Then

  1. if a person believes that m1 and m2 are members of a series of successive particulars in which every one of a certain set of properties P1, P2, . . . Pn are present, he will be inclined as a rule to call ml and m2' the same thing'.
  2. Unless he believes ml and m2 to be members of such a series he will not as a rule be inclined to call them 'the same thing'.
  3. If he positively believes that all series of which m1 and m2 are members lack one or more of these characteristics, he will be disinclined as a rule to call them 'the same thing'. But there is no set of properties P1, P2, . . . Pn such that
    1. a person who believed that m1 and m2 are members of a series having all these properties would be speaking incorrectly if he said 'm1 and m2 are not the same thing'; and such that
    2. a person who believed that every series of which m1 and m2 are members lacks one or more of these properties would be speaking incorrectly if he said 'm1 and m2 are the same thing'.

      In view of the difficulty of finding any set of properties which could be taken as the conventional connotation of the phrase 'same thing at different moments' -- a difficulty which is well brought out by Marc-Wogau's examples -- I think that it is probably wise to state the theory in this carefully guarded way.

      There is one other point to be noticed before we leave this topic. Marc-Wogau raises the question whether there is not a logical circle in making continuous spatio-temporal connexion between the material thing which occupies s1 at t1 and the material thing which occupies s2 at t2 a condition for calling them 'the same thing .

      The difficulty may be put as follows. Suppose that m12 and m23 are adjoined in time and that they occupy the same or adjoined positions in space. Can we attach any meaning to the latter part of this statement except the following? (i) That m12 stands to a certain other material thing M12 (which is contemporary with it) in a spatial relation which is the same as, or only slightly different from, that in which m23 stands to M23 (which is contemporary with it); and (ii) that M12 and M23 are called 'the same material thing'. If so, will not precisely the same question arise about M12 and M23, viz., what induces us to call them 'the same material thing'? If we give the same kind of answer, we shall be referred to M12' and M23', and the same question will arise about them. And so on to infinity.

      Marc-Wogau's answer is that each of us has a sense of position and orientation which is independent of reference to his own or to other bodies. Each of us is aware of surrounding space as a 'structural whole', in which he can distinguish determinate positions even when no external object is visible, and can recognize them again even when he has moved. In particular one recognizes the distinction between vertical and horizontal independently of the orientation of one's body at the time. It is true that the distinction left-right and behind-or-in-front are essentially relative to one's body. Yet even in that case a rotation of one's body is experienced as a movement of it within a fixed surrounding space. After having turned through an angle with one's eyes shut one can still indicate the direction, relative to the present orientation of one's body, in which an object, formerly seen straight in front of one, now lies. For these reasons Marc-Wogau thinks that the objection of circularity fails.

      I have no wish to deny either the alleged facts or their importance for the phenomenology of spatial perception. But I wonder whether they constitute an answer to the original difficulty. That is concerned with physical things in public space, and not, e.g. merely with the location of visual prehensa in the visual fields of those who prehend them. Now, in spite of the phenomenological facts which have been adduced, does it not remain true that the location of physical things and events in public space is accomplished only by referring them to certain bodies chosen as a system of reference?

(2) Unity of a Thing in relation to the Plurality of its Contemporary Aspects.

      Consider the examples of the two persons who look at the same cube from opposite sides of the table; and the two persons who look at a penny, one from near-by and perpendicularly, and the other from a great distance and in a very oblique direction. There is a sense in which the two observers in each case see different objects. But we also use language which seems to imply that they see the same object; for we say that the two observers in the first example 'see the same cube' and in the second 'see the same penny'.

      The problem presented by these examples can be put in either of the following alternative forms.

  1. How can two different co-existent objects, e.g., the faces F1, F2, and F3 and the faces F3, F4, and F5 of the cube, or the round-looking unforeshortened-looking object and the elliptical-looking foreshortened object, be one and the same thing, viz., a certain cube or a certain penny?
  2. How can we say that two observers 'see the same thing' when we admit that they see different objects?

      Marc-Wogau says that the problem is most acute in such cases as the example of the two observers of the penny. In the cube-example common-sense would accept the answer that, in the strictest sense of 'see', each observer sees only a part of the cube, and that the parts seen by the two only partially overlap. In the case of an object seen both directly and in a mirror common-sense would admit that what is expressed by saying 'I saw such and such an object in the mirror' would be more accurately expressed by saying 'I saw in the mirror a reflected image of such and such an object'. But common-sense is not inclined to admit that it would be more correct to say that the remote observer of the penny from a very oblique direction saw a very small elliptical object. It insists on saying that he saw the same round moderate-sized object as was seen by the other observer, but that it 'looked elliptical and foreshortened to him from where he was standing'.

      The essence of Marc-Wogau's analysis is to be found on pages 102 to 118 of his book. It may be stated as follows. The phrase 'the thing T at the moment t' is applied, not to a single particular, nor to a certain set of inter-related particulars taken as a collective whole, but distributively to every one of a certain class of particulars. This class may be subdivided into two parts, which may be called the 'nucleus' and the 'fringe'. For the present we will confine our attention to the nuclear members. The fundamental feature of these is that they differ from each other only abstractively. (The objects prehended by the two observers of the cube would be nuclear. The object prehended by the person who looks at the penny very obliquely from a great distance would be non-nuclear.)

      Marc-Wogau considers two alternatives to this analysis.

      (i) One is that the thing should be identified with such a set of abstractively different particulars taken collectively. He points out that, on this analysis, it must be admitted that a person can never see a thing in the sense of visually prehending it. Such a sentence as 'I see a cube' will have to be translated into something like 'I visually prehend a certain member of a certain set of particulars which differ only abstractively from each other'. Marc-Wogau does not profess to refute this suggestion. But he thinks that it should be avoided, if possible, because it forces us to put such an out-of-the-way interpretation on many facts which are prima facie quite straightforward.

      (ii) It might be alleged that the thing is something more concrete than any of these objects, and something to which they all stand in a common relationship. It might therefore be suggested that the phrase 'the thing T at the moment t' applies only to the one completely concrete member of a certain set of particulars which differ only abstractively from each other. To this MarcWogau answers that such a set of more and more concrete objects which differ only abstractively from each other is in principle infinite. So the notion of a thing as the one completely concrete member of such a set would be the notion of a common upper limit to a number of series which all converge on it, and not the common last term of all such series.

      I suppose that Marc-Wogau's objection to this is that any 'material thing' would then be a kind of Platonic Idea, laid up in Heaven, and once more not the kind of object that could be 'seen', in the sense of visually prehended.

      To this one might be inclined to retort as follows. Why not say that the material thing is the one actual concrete existent in connexion with such a set of particulars, and that the other members of the nucleus are all abstractions from it in the following senses?

  1. Each is only a part of its surface.
  2. Each is visually prehended only as having certain characteristics, though it in fact has others also which cannot be visually prehended or cannot be prehended at all.
  3. Each is visually prehended only as coloured, shaped, etc., in an incompletely determinate way, though in fact it is qualified completely determinately.
This is at least less odd prima facie than to hold that there are particulars which are incompletely determinate in their qualities, and are not merely prehended as qualified more or less indeterminately.

      We return now to the original suggestion that such a phrase as 'that penny there now' applies distributively to every one of a certain set of particulars which differ only abstractively from each other. Marc-Wogau remarks that we can ascribe, in a certain sense, to each member of such a set the properties of every other member of the set, and not only those properties which it is prehended as having. Thus, e.g., we can say that the object prehended by a person, who merely looks at a block of ice without touching it, is cold, although of course he does not visually prehend that object as cold. But all such statements are analyzable on the following lines: 'This particular, which I visually prehend only as translucent and as a certain part of the surface of a cube (and which in fact has only those qualities), differs only abstractively from certain other particulars which co-exist with it in the same place and are cold'. We might sum up this part of the theory as follows. To prehend in any way any member of such a set of particulars is ipso facto to perceive mediately any other member of the same set, and therefore to perceive mediately all the more concrete members of that set.

      Now I think it is important to contrast this analysis with the following prima facie possible alternative, which the terminology introduced at the beginning of this paper was meant to leave open. It might be suggested that the very same particular, which I visually prehend only as translucent and as a certain part of the surface of a cube, has also other properties, such as coldness and smoothness, which I cannot visually prehend; and that it has them in the same literal and non-dispositional sense in which it has the translucency and the cubical contour which I visually prehend it as having.

      It should be noted that Mare-Wogau's dictum that abstracttive difference involves numerical difference does not suffice by itself to rule out this alternative. What is required in order to rule it out is the following premise, viz., that a characteristic which a particular is not prehended as having cannot belong to it in the same literal non-dispositional sense in which a characteristic which it is prehended as having does so. On that assumption a particular which is prehended as translucent, and is not prehended as cold or smooth, must be a different particular from any which would be prehended as cold and smooth if it were prehended at all.

      It remains to mention the non-nuclear members of that set of particulars to each member of which the phrase 'the thing T at the moment t' is applied. We say that the remote observer who looks at the penny very obliquely is seeing the same penny as the near-by observer who views it from above. But here the former observer prehends his prehensum as having certain characteristics which are incompatible with those which the latter prehends his prehensum as having. The difference is qualitative and not merely abstractive. Associated with this is another difference. The nuclear members exist in the sense E3; the non-nuclear members exist only in senses E1 and E2.

      It does not appear to me that the last statement adds anything substantial. For the distinction between these two senses of 'existence' is not independently defined; it is introduced and illustrated simply by reference to the contrast between such cases as the two observers of the penny.