In my studies this week, I was stuck on the following passage from Aristotle: “In other things, therefore, it is demonstrated after the same manner through conversion, that the conclusion is necessary, just as in existing or being present with a thing.” I wrestled with its meaning, or rather what its point was. After re-reading the chapter, and after many dialectical sessions with the tutor, a workable interpretation came to the surface of my mind.
I noticed that in the prior passage Aristotle is speaking of privations: “For a privative assertion is in a similar manner converted, and we similarly assign to be in the whole of a thing, and to be predicated of every.” The more I thought about it, the more I came to the conclusion that a confirmation of what something is not, could not be a certain demonstration of what that very same thing is. E.g. the propositions ‘no B is A’, and ‘no A is B’, co-witness a universal privation that both A and B are not each other. However, we have not ascertained what A and B are. On the other hand, the first figure syllogism Barbara demonstrates what A and B are: viz. ‘every B is A’, and ‘some A is B’ post-conversion.
Therefore, in my notes, I wrote the following to summarize this passage: “What is affirmatively necessary, conclusively, is demonstrated by conversions.”
EAR