Avicenna on necessity and possibility

Avicenna famously says that God is 'necessary in himself', while all creatures are both 'possible in themselves' and 'necessary from another'.

There are two distinctions here.

1. The first distinction is between something that is 'necessary in itself' and something that is 'possible in itself'. God is 'necessary in himself', while everything else is 'possible in itself'.

It would be a mistake to interpret this as a distinction between necessary and contingent beings, as if that which is 'necessary in itself' exists in every possible world, while that which is 'possible in itself' exists in some but not all worlds.

This would be wrong not only because Avicenna doesn't believe in possible worlds (for Avicenna, there are no possible worlds -- just the one, necessary world), but also because Avicenna thinks everything that is 'possible in itself' is produced necessarily. Since anything that's produced necessarily would exist in every possible world, it would be incoherent to also say that it would exist in some but not all worlds.

(Averroes thinks Avicenna is suggesting just that, so he accuses Avicenna of incoherence. But Averroes' interpretation is incorrect.)

So we should not think that to be 'possible in itself' means to be 'contingent'. Rather, we should take it to mean just what Avicenna says: that which is 'necessary in itself' exists without being produced, while that which is 'possible in itself' exists because it is produced.

And that, I think, is the bottom line. That's all that Avicenna means when he talks about being 'necessary in itself' and 'possible in itself'. There's nothing there about modality.

Now, Avicenna says some other things about being 'necessary' or 'possible in itself', but I don't think they take away from my point. They are as follows.

(a) Something is 'necessary in itself' if its non-existence entails a contradiction. In other words, something that is 'necessary in itself' is the sort of thing that simply must exist. Consequently, it exists on its own, so it need not, and in fact it cannot, be produced. (It just exists on its own, and you can't produce what already exists.)

(b) By contrast, if something is produced, then it cannot be 'necessary in itself'. If it were 'necessary in itself', then it would exist on its own, so it could not be produced. But since it is produced, it must not be 'necessary in itself'.

(c) Further, since it's produced, it must not be 'impossible in itself', for impossible things cannot exist at all.

(d) Its existence, then, must be within the bounds of possibility. So it is 'possible in itself'.

But as I said, I don't see how any of that takes away from the basic point: for Avicenna, to be 'necessary in itself' means to exist without being produced, and to be 'possible in itself' means to exist because its produced. And that's all it means.

Some people talk as if Avicenna thinks there is a realm of 'possibles' standing in front of God, and God chooses what to actualize.

But I don't think that's right either. Avicenna uses the word 'possible' only because that which is produced is neither 'necessary' nor 'impossible' in itself, and the only word left is 'possible'. But unfortunately, the word 'possible' suggests contingency, a realm of 'possibles', etc.

I think a better label would be 'not necessary in itself'. Avicenna's real point is just that a product is produced; it's not the sort of thing that just exists without being produced. As Aquinas nicely puts it in Sent. 1.8.3.2: 'That which acquires its existence from another does not exist necessarily in itself, as Avicenna proves'.

So to say that something is 'necessary in itself' means nothing more than that it exists without being produced, and to say that something is 'possible in itself' means nothing more than that it exists because it is produced. That's it. No modality here.

2. The second distinction, however, does have to do with modality. This is a distinction between something that is produced necessarily and something that is produced contingently (or, in Avicenna's terminology, between what is 'necessary from another' and what is 'possible from another').

For those who believe in possible worlds, we could put the point like this: a product is 'necessary from another' if it's produced in every possible world, but it is 'possible from another' if it's produced in some but not all worlds.

Note that just because something is produced does not entail whether it is produced necessarily or contingently. To put it in terms of possible worlds again, a product might be produced in every world, or it might be produced only in some.

This is why I say that the distinction between being 'necessary' or 'possible in itself' is not a distinction between necessary and contingent beings. It is just a distinction between being produced or unproduced. The distinction between being necessary or contingent comes up here, i.e., in the distinction between being 'necessary' or 'possible from another'.

For reasons I don't want to go into here, I should note that Avicenna's distinction between being 'necessary' or 'possible from another' is only a logical distinction. Avicenna believes that every product is produced necessarily, so there is nothing that is genuinely contingent in Avicenna's universe. So the distinction is just logical.

Nevertheless, the point still stands: to be produced is one thing, and to be produced necessarily or contingently is another. Again, to put it in terms of possible worlds, a product cannot exist in a world all by itself: if it exists in a world, it must exist with its producer. But that says nothing about how many worlds a product exists in. It might exist in none (if it was never produced), it might exist in some if it's produced contingently), or it might exist in all (if it's produced necessarily).

Obviously, the distinction between being 'necessary' and 'possible from another' only applies to products. It cannot apply to something that is 'necessary in itself', for such things are not produced, so there's no option to be produced 'necessarily' or 'contingently'. Only products can be produced 'necessarily' or 'contingently'.

Consequently, anything that exists without being produced has only the one feature: that of being 'necessary in itself', while anything that is produced has two features: that of being 'possible in itself', and that of being 'necessary' or 'possible from another'.