Thanks to Stephen for this post!
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A problem that has troubled me for some time concerns our knowledge of powers. Powers are supposed to be perfectly naturalistic elements of our world and accordingly should be epistemically accessible in theory. This is important for a couple of reasons. One is that we need to respond to Hume’s view that we can have no notion of power over and above constant conjunction, which is what he thinks we experience. And those who enthuse about powers do so partly because, contrary to what Hume says, they think powers are familiar to us. This provides an alleged advantage over those metaphysics that depend on other possible worlds, all of which are – as the theory accepts – epistemically inaccessible to us.
A possible hitch, though, is the argument that powers are themselves unknown. All we can really know, goes the objection, are the manifestations of those powers. One of the basic moves of the powers theory is to distinguish sharply between the powers and their manifestations. Powers are directed towards their manifestations, in some sense, and can exist without them. We can see that the glass is broken or the sugar is dissolved; but can we see that these things are fragile and soluble? Perhaps not. A force may push against your body; but arguably it is only the manifestation of the force that you feel, not the force itself. And if we concede that it is indeed only manifestations that are experienced, rather than the powers, then we seem to play into Humean hands. They are the ones who tell us that only the events exist: no hidden powers behind them, generating them. So if we concede that we have no experience of the powers themselves, the Humean can invoke their old argument that we have no right to speak of powers as anything over and above the pattern of events we experience.
I offer two thoughts on this issue, from the viewpoint of a friend of powers. First, maybe the powers just are theoretical postulates lying behind their known manifestations. But that shouldn’t in itself condemn them. It just means that their status as entities is metaphysical and, like anything else metaphysical, we should believe in their existence on metaphysical rather than empirical grounds. It is arguable that powers can be known to exist if there are valid metaphysical arguments for their existence. A realist metaphysicist is unlikely after all to say that empirical evidence is the only good ground for belief in something.
I think this first response is certainly attractive but it doesn’t really address the concern. In particular, there was a claimed advantage of powers over possible worlds, but they now look to be in the same epistemic boat: known only as theoretical postulates, justified in terms of their explanatory role.
The second point might get more to the heart of the matter. It seems unfair to treat the powers standing behind manifestations as entirely epistemically unknowable when the grounds for doing so would not usually apply to other known entities. Powers are known through their effects, in this case their manifestations; but so is everything else and we don’t take that as a compelling reason for general scepticism. So if we reason that a power cannot be known, only its manifestation, shouldn’t we argue that a table cannot be known, only its effect on our senses, and the same for every other thing we perceive?
Perception occurs through the perceiver being causally affected by the object of perception; in other words, things are known through their effects. Beliefs in unperceived objects and in substances as causes of perceptions are thus metaphysical beliefs, inferred from the effects that such objects have on us in perception. Yet the experiences caused in us by a table, for instance, are as good empirical grounds as any to say that we have knowledge of the table: not just knowledge of the effects of the table. This seems sound reasoning especially if you have a broadly Eleatic view about the nature of existence. To be real is to be causally powerful and to be known empirically is nothing more than to enter into some kind of causal relation with a knower: to affect it. Being affected by something is thus an essential part of the story of what it is to know it. Just as one knows a table from its manifestations, shouldn’t we say the same of all powerful entities: they are known by their effect?
What, then, of the powers themselves? Are they to be excluded from this thinking because they are the things standing behind and causing experiences? I am not sure that is fair. And should we then concede to the Humean that they are right that the world consists of nothing but a pattern of manifest events? This move still might be resisted. To say that manifestation in perceptions is the way in which a thing is known is not to say that the thing is nothing but those manifestations in perception. That seems to be the fallacy committed in phenomenalism about objects, such as in Berkeley’s system. If the proposed analysis is right, then it seems at least a possible position to allow that powers are known and experienced, through their manifestations, but are nevertheless distinct from those manifestations. I confess that my thinking on this topic remains incomplete.