## Friday, December 13, 2019

### Joint powers

Suppose neither Alice nor Bob has the power to budge the sofa, but together they can lift it. Causal powers belong to substances, and Alice and Bob do not compose a substance, so it seems the causal power to lift the sofa does not belong to the pair as a pair. Rather, the power must belong to the pair in virtue of the substances composing it. But how can that work?

Here is what I used to think. Causal powers come with actuation conditions. So we can say:

1. Alice has the power to lift the sofa when Bob is helping.

2. Bob has the power to lift the sofa when Alice is helping.

But now suppose both are working together. Then both causal powers’ actuation conditions are met. But when each of two causal powers for an effect E is actuated, then E is overdetermined. Thus, the sofa’s upward movement is overdetermined. But that is clearly false. So something is wrong.

Maybe we just need a better account of overdetermination? Or maybe there need to be irreducibly joint powers?

William said...

Why should only persons have powers? Don't nations have powers that are not held by any single citizen of that nation?

Alexander R Pruss said...

There are no nations in the correct fundamental ontology. :-)

Note, too, that there is a difference between having a power not held by any part and having a power not *reducible* to the powers of the parts.

William said...

Well, perhaps the resolution to the table problem is to say that there is no table, just as there are no nations. So the power of lifting is not of a table, but of part of the mass of the thing called a table that is not in the ontology.

Though I wonder if this does not start to look like a reductio of the limited ontology at some point.

SMatthewStolte said...

Maybe we should say that Alice has the power to partially lift the sofa when Bob is helping. (I think there’s no such thing as partially lifting without help. If the thing is too heavy to get off the ground, pulling up isn’t lifting at all.) Is this what it would mean to talk about irreducibly joint powers?

Atno said...

I think Bob and Alice jointly contribute to the actualization of a single power. When you combine Bob and Alice, you get that power. Not very different from causation in general; a match does not by itself literally have a power to produce fire, but it has some power by itself, and other substances and environmental conditions have other powers which "add up" to fire combined with the match, etc.

AMC said...

Is there a problem with defining power in terms of ability to exercise a certain physical force?

So, in order to move a sofa, a certain number of units of (directional, mostly upwards) physical force must be applied to the sofa.

Each of Bob and Alice (on their own) can only exert less units of physical force on the sofa than is required to move it.

Any substance, or combination of substances (whether Alice and Bob or anything else), can only move the sofa when the (or at least the) requisite units of physical force can be applied to the sofa.

Wouldn't you just say at if any single substance or multipllicity of substances is/are to move the sofa, then that single substance or multiplicity of substances must be able to exert the requisite units of physical force on the sofa?

Jonathan D. Jacobs said...

What would be wrong with thinking something like this? Powers are powers to do very specific things. (Our ordinary concepts don't concern themselves with all the details.) Most of the time, powers are powers to *jointly cause* things. (In our world, things rarely, if every, act alone.) Many of the things we normally think of as "actuation conditions" are really just potential joint causes. So Bob has a power to jointly cause the movement of the sofa, and that power is massively multi-track: the power to jointly (with Bob, the earth's gravitational pull, the atmospheric conditions, etc., etc.) cause the sofa to move in thus-and-such a specific way, the power to jointly (with Bob and Sara and . . .) cause the sofa to move in this-other specific way, etc., etc.

Alexander R Pruss said...

Jonathan:

I think it depends on how one works out the details of the proposal. Consider two variant ways of parsing:

1. Bob has the power-jointly-with-Sara to cause the sofa to move.

2. Bob has the power to-jointly-with-Sara-cause the sofa to move.

If we go for 1, then I have a hard time distinguishing this from the actuation condition story that leads to overdetermination. If you want to go for 1, maybe you can spell out a bit more to help me see how this differs from Bob having the power to cause the sofa to move in the circumstance of Sara helping.

If we go for 2, then I think we have potential falsity: Bob needn't have the power to make it be the case that jointly with Sara he causes the sofa to move. For to have that power, he would have to be able to *make* Sara cooperate.