why you don’t need to know everything in order to know something:

according to Aristotle, some (ie Speusippus) thought that in order to know something, you had to know what makes it different from other things.

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but differences are mutual. so in order to know what makes A different from B, I need to know what B is. and I need to know what C is, etc. otherwise I can’t know what A is! which is frustrating.

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as an example, if I want to know what a human is, I need to know what makes humans different from cows. but in order to do that, I need to know what makes cows different from fish. and fish different from...etc. obviously, none of us know all this stuff

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Aristotle responds: no, you can know what something is without knowing what literally everything else is. why? because there is a difference between a unique differentia and differences

4/n

to know what a human is, I need to know what makes a human a human. I don’t need to know what makes a human different from a cow. what makes something what it is is called its ‘differentia’ or its specific difference.

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of course, if I know what a human is, I *will* know (one of) what makes a human different from a cow. but that’s just a consequence of knowing what a human is. it’s not the requirement to know what a human is.

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so in order to know what a human is, I need to know what is specific to her: rationality. from this, I know that cows, fish, boxes etc are all not rational. but I don’t need to know what makes a cow uniquely a cow or different from a fish.

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in order to know that a human’s specificity lies in rationality, I need to be able to know what rationality is, but again, that doesn’t mean that I have to compare humans to every other animal.

8/n

in order to know THAT humans’ specific difference is rationality, you might need to compare humans to animals. but you also might need to compare humans to themselves. and you also can’t just list out what makes humans different from animals, or what is consistent across humans

sometimes, things are consistent between humans but they aren’t what make us specifically different from other things. for example, humans laugh. but laughter isn’t what makes us what we are. so determining the essence of a thing is a pretty tough business

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