TROUBLE WITH PROPOSITIONS The premises of argument are embodied in propositions -- sentences that set forth the claims made about the materials. Sometimes these propositions assert that certain conditions obtain. The conditions are well enough understood, but the claims made are exaggerated or unwarranted in some other way. Perhaps they are too broad -- all fire engines I have ever seen are red, but I leave out the qualification ("I have ever seen") and simply state "All fire engines are red." Sometimes the relationships among the facts are misinterpreted -- I eat lobster and have nightmares, so I announce as though it were a universal law: "Lobsters cause nightmares." If a speaker takes certain well understood precautions, he can avoid unwarranted claims in his premises.
In this section we assume that the materials are as well in hand as they are likely to be, or at least as is necessary for making responsible assertions about them. The troubles treated in this section, then, come from going beyond or counter in some way to the evidence. In the next section "Trouble with Constructions," the troubles are more subtle, since they are interferences encountered in the actual formation of the notions about the evidence, related together or otherwise modified in the propositions. For the present we assume that the constructions are suitably precise and that the problems come from their use in propositions, rather than from their formation in experience.