Timeline Philosophers Arguments in Ordinary Language People reasoning in ordinary language rarely express their arguments in the restricted patterns allowed in categorical logic. But with just a little revision, it is often possible to show that those arguments are in fact equivalent to one of the standard-form categorical syllogisms whose validity we can so easily determine.
Some birds are geese.
Therefore, Some birds are not felines. In slightly more complicated instances, an ordinary argument may deal with more than three terms, but it may still be possible to restate it as a categorical syllogism. Of course, we need to be perfectly certain in each case that the expressions are genuinely synonymous. Second, if two of the terms of the argument are complementary , then appropriate application of the immediate inferences to one of the propositions in which they occur will enable us to reduce the two to a single term. Some pets are not dogs.