Classical formal logic constitutes one ambitious attempt to capture every logical form of argument in a single language. Equally, the basic elements of the logicians’ formal language can also be combined in certain ways, according to some simple grammatical rules, and combinations of basic elements can be separated out, again according to simple rules. For the plain truth of the matter is that prepositional logic is the logic of sentences formed from sentence-letters, by the appropriate rules, using what logicians call an adequate set of connectives. The distinction between premises and assumptions is again one which is often glossed over in introductory logic texts but it is a good distinction none the less: premises are explicitly asserted to be true and conclusions are proved from them. Such reasoning is categorical reasoning.