Random Philosophy

[lorimt]

I juts ran across this while reading Avicenna.

"Moreover, if any thing is composed of two things, if one of the two things cam be found without the other, the other can be found without the first. An example of this is oxymel, which is composed of vinegar and honey: if vinegar can be found without honey, honey can be found without vinegar. Another example is the formed statue composed of bronze and the human form: if bronze can be found without the human form, the human form can be found without the bronze. This can be found by induction and has many examples."

I'm not buying into the induction bit without an actual proof, since I've seen too many 'proofs' of this sort by ancient philosophers. The concept, however, strikes me as very interesting, particularly the form/material bit. Does anyone have any counterexamples, or particularly interesting examples? My brain is wavering between "I've got it, it all makes sense, look how obvious this idea is," and "What about this case? This isn't true at all."

Of all the Avicenna I've worked through tonight, this was the bit that most caught my eye. It sort of sums up the rest however. I've found a tendency to alternate between "how interesting," and "you make no sense," though usually in regards to different arguments.

Comments

[kitty-tape.livejournal.com]

I don't think this works because it is saying if there exists an A without a B then there exists a B without an A. Now, if you said if for all A, A exists without B then, if B exists, there exists B without A. An example as to why the quantifier must be treated this way is as follows: if water can be found without a duck, then a duck can be found without water. This is clearly false if we consider that a duck is composed of water and therefore cannot be found without it. (Clearly, we can find water without a duck; it is what I prefer to drink.)

[lorimt]

I don't think it is quite so general. I think the only case being specified is where one item is made of two things.

Now, your example could be rewritten to say that a duck is composed of water and duck bits that aren't water, and that water exists independantly, where duck bits without water don't. (Even if you dehydrate duck, but I don't think that context is supposed to exist.) Even so, I don't think this is necessarily what the author is intending by this. Actually, I retract my parenthectical comment above. Perhaps Avicenna did mean the equivalent of dehydrated duck bits. I *think* the thing he is trying to get at with that is that if you can concieve of a thing A as being made up of two separate things B and C, then B and C must exist independantly. (The separate bit means that B and C can't secretly be the same thing.)

The part I'm having difficulty with most is if you have some substance that can only be found in combination with other substances, and I can't think of any such example. Perhaps oxygen and fire. Oxygen can exist independant of fire, but only the concept of fire can exist without oxygen. Grr, but that doesn't fit the having one object made up of two parts thing. I've almost got my brain wrapped around this, really.

[telso.livejournal.com]

Although I can't find it anywhere on google, I remember my chemistry textbook stating that ammonium ions have never been separated from water, that they always coexist with hydroxide ions and water and ammonia, the last two making up about 99% of the mixture. If you try to take away water or ammonia, the reaction just shifts to produce more water and ammonia. And since the ratio of equilibrium is around 99 to 1, if you take away all the water or all the ammonia, all the ammonium ions will react and so there will be none left (and if you try to collect the ammonium, the ammonium you take will just react with hydroxide and change into water and ammonia). Although you can have compounds not in water with ammonium, they aren't ammonium ions.

So in this case ammonium has to exist with water, ammonia and hydroxide ions while each of those substances can exist without ammonium ions. However I'd check this information before you go to argue with your teacher.