Friday, December 19, 2008

Aristotle on Opposites 2: Contraries

Last time, I talked about the first kind of 'opposites' that Aristotle talks about in the Categories 10, namely 'correlatives'. Correlatives are relational features that are reciprocal, like 'double' and 'half' (each refers to the other).

The second kind of 'opposites' are what Aristotle calls 'contraries'. These are what we typically think of when someone says, 'give me an example of a pair of opposites'. 'Hot' and 'cold', 'good' and 'bad', 'black' and 'white', 'healthy' and 'sick', things like that.

Here in Categories 10, Aristotle says two things about contraries.

(1) Contraries are not relational and reciprocal. They do not each relate to the other in the way that 'double' and 'half' do. If something's 'double', then there must be something else that's 'half'. A 10kg block couldn't be 'double' if it were the only thing in the universe, for there'd be nothing it could be the double of. But if something's hot, then there's no guarantee that something else will be cold. A candle could exist all by itself, and it'd still be hot. Hell, even if one thing is hotter than another, the cooler of the two still needn't be cold.

Of course, contraries like 'hot' can stand in various relationships -- this bit of heat might be double the temperature of that one -- but the contraries themselves are not relational features like correlatives are. Contraries are, I reckon, non-relational features.

(2) Contraries are divided into two broad groups.

(a) In the first group belong all that are necessary and binary. A pair of contraries is necessary if the appropriate sorts of things always have one or the other (but not both), and never neither. (I say 'the appropriate sorts of things' because contraries don't belong to just any old thing. Only certain kinds of things can have certain kinds of contraries. Animals can be healthy or sick, but stones cannot.) A pair of contraries are binary if those two contraries are the only options, and there's nothing in between.

For example, health and sickness are necessary and binary in this sense. Every animal must be either healthy or sick, but never neither, and it can't be somewhere in between. (Of course, we might say that an animal is 'in between' in the sense that it's partly healthy and partly sick, but that applies to different parts of the animal, not the same part.) Similarly, 'odd' and 'even' are necessary and binary for whole numbers (except zero). Every whole number (apart from zero) must be either odd or even, and it can't be somewhere in between.

(b) In the second group belong all contraries that are neither necessary nor binary. White and blackness, for example, are not necessary, nor are they binary. Animals can be white, black, or anywhere in between.

Aristotle speaks as if the division between (a) and (b) is exhaustive. All necessary contraries are binary, and all unnecessary contraries are not binary. There are no necessary contraries that are not binary, and there are no unnecessary contraries that are binary.

That's all Aristotle says in Categories 10. It doesn't give us a whole lot to go on. I still wonder what it is, exactly, that makes two things contrary? Elsewhere, Aristotle says that contraries are what are 'the most distant in the same genus' (Categories 6, 6a15-18). That is, if we take any particular kind of feature that comes in a variety of degrees, the two ends of the spectrum are the contraries. For example, color comes in different shades ranging from black to white, but since black and white sit at the ends of the color spectrum, black and white are the contraries for color.

But that won't do; not quite. Aristotle thinks some contraries are binary; for them, there's nothing in between, so there's no spectrum. Consequently, we can't talk about a 'spectrum', or a 'variety of degrees', or anything like that. Instead, we need to talk about contraries as the two most different features that belong to the same kind. So even if there were no colors except for black and white, black and white would still be contraries because they're the most different of any two colors. And that would work for any feature-kind, no matter how many different features belonged to that kind.

However, this would mean that every two-membered feature-kind is a contrary. Would Aristotle accept that? I don't know. But more importantly, this would mean that all two-membered feature-kinds are necessary, for those kinds would be binary, and all binary contraries are necessary. Conversely, any more-than-two-membered feature-kinds would be unnecessary. I'm not sure whether Aristotle would accept this implication. Maybe he would. I don't know.

Before I finish, there are two little problems to bring up.

(i) A short while later in the Categories (see 12b37-13a2), Aristotle says that some contraries are essential constituents for certain kinds of things. For example, whiteness is an essential constituent of snow, because snow is always white. Doesn't this mean that whiteness is necessary for snow? If so, it should follow that whiteness belongs to a pair of binary contraries (for Aristotle has said that all necessary contraries are binary). But that's obviously false. There are other colors besides white and black. On the one hand, then, Aristotle says that all necessary pairs are binary, but on the other hand, he says some necessary pairs are not. Which is it?

(ii) Aristotle also says a little later (see 13a31-37) that contraries are variable: something can switch from one contrary to the other (a pot can become hot, then cold, then hot again). He makes this point in order to distinguish contraries from the third kind of opposites: namely, possessing a natural ability, and being deprived of that ability. Possession and deprivation, says Aristotle, are permanent (once blind, a man doesn't regain his sight), and since contraries are variable, they're not the same as possession/deprivation. Now, if some contraries are necessary constituents for certain things (as whiteness is for snow), then surely those are 'permanent'. Again, then, it seems that Aristotle is saying that contraries are 'variable', and that they're 'permanent'. Which is it?

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