  It turns out that some of these arguments are deductions, or valid syllogisms, and some are not. Those which are not admit of counterexamples, whereas those which are, of course, do not. There are counterexamples to those, for instance, suffering from what came to be called undistributed middle terms, e.g.: all As are Bs; some Bs are Cs; so, all As are Cs (all university students are literate; some literate people read poetry; so, all university students read poetry). There is no counterexample to the perfect deduction in the form of a universal affirmation: if all As are Bs, and all Bs Cs, then there is no escaping the fact that all As are Cs. So, if all the kinds of deductions possible can be reduced to the intuitively valid sorts, then the validity of all can be vouchsafed. 