PHIL2206 Philosophy of Mind
Week 8: Mental Causation

Mental causation

  1. As we have already discussed, there seems to be such a thing as mental causation: mental events can cause and be caused (and indeed sometimes are).
  2. Indeed, if mental causation were not possible then that would have some drastic consequences:
  3. Quote from Jerry Fodor on page 181 of Kim.
  4. As we have seen, the possibility of mental causation is a big problem for substance dualism.
  5. This week we'll see that it's also a problem, or at least seems to be, for substance physicalism as well (the most popular alternative to substance dualism).
  6. While it is popular to think that there are all three kinds of causation, mental-to-physical, physical-to-mental, and mental-to-mental, there are alternative views:

Davidson's anomalous monism

  1. There is a nomological theory of causation, according to which causally connected events must be subsumed under a law. More precisely:

    For all events e1 and e2: if e1 occurred and e2 occurred after e1, then e1 was a cause of e2 only if there are kinds k1 and k2 such that: e1 is of kind k1, e2 is of kind k2, and it is a law that events of kind k1 are followed by events of kind k2. (Let's say that in this case the law covers e1 and e2.)

  2. According to this view, for the heating of a metal rod (event e1) to cause the expansion of the rod (event e2), there must be a law covering e1 and e2. Here is one possibility: Metal expands when heated (i.e. events in which metal is heated (kind k1) are followed by events in which metal expands (kind k2)).
  3. If this view is right, then a mental event, e1, can be a cause of a physical event, e2, only if there is a law covering e1 and e2.
  4. Donald Davidson has argued that there are no laws covering mental and physical events - there are no psychophysical laws.

    Well, almost: there are no laws covering intentional mental events (believings, desirings, hopings, intendings) and physical events.

    This is Davidson's anomolism of the mental. We'll look at his argument soon.

  5. If the nomological theory of causation is correct, and if there are no laws covering intentional mental events and physical events, then it seems that intentional mental events cannot cause physical events. It seems that the following cannot all be true:
  6. But Davidson argues that they can all be true.
  7. How? By postulating that intentional mental events are also physical events - as well as falling under a mental kind, they also fall under a physical kind. And so they can cause physical events, because there are laws covering physical events and physical events.
  8. We can strengthen this proposal: that all mental events are also physical events. This is Davidson's monism. Together with his anomolism of the mental we get his anomolous monism. The picture is this: the world is composed exclusively of physical objects and physical events, but some physical events are also mental events (i.e. fall under mental kinds).
  9. Davidson sees this as a version of the identity theory (but of the boring token-token kind?). And he thinks that he has here an argument for it: it is a way of reconciling the three claims above.
  10. Why does he believe in the anomolism of the mental? He argues as follows:
    1. When we ascribe intentional mental events to a subject we must do so according to the following principle: the total set of intentional mental events that we ascribe should make the subject as rational and coherent as possible. In other words, it is not possible to ascribe intentional mental events one-by-one - it must be done holistically.
    2. Suppose there were a psychophysical law, say the following one: a neural event of kind k1 occurs in a subject s at time t iff an intentional mental event of kind k2 (say, a believing that Krsitina Kenneally is gorgeous) occurs in s at t. Then we could ascribe intentional mental events one-by-one, just by observing neural events.
    3. So there are no psychophysical laws.
  11. Here is a concern about Davidson's anomolous monism:

    Suppose your desiring to drink water (a mental event) caused your turning on of the tap (a physical event). If Davidson is right, this is only because the first event falls under some physical kind (in addition to a mental kind); that is, because it has some physical property (in addition to a mental property). So it seems that the only properties of the first event that are causally relevant are its physical properties - whatever mental properties it happens to have are causally irrelevant. But then in what sense have we saved mental causation?

  12. Here is a concern about his support for it:

    We should reject the nomological theory of causation.

    One alternative is a counterfactual theory of causation. Here is a starting version: Event c was a cause of event e iff (a) c and e occurred, and (b) if c had not occurred then e would not have occurred.

    We will not discuss this here (see Kim).

The exclusion argument

  1. There is an argument, the exclusion argument, that there is no mental-to-physical causation.
  2. The argument appeals to two principles (i.e. takes them as premises).
  3. First principle (the closure principle):

    If a physical event e has a cause, then it has a physical cause, and moreover it has a sufficient physical cause: there is a physical event e' which occurs and causally necessitates the occurrence of e.


    (Note that the biological domain is not causally closed: radiation causes cells to mutate.)

  4. Second principle (the exclusion principle):

    Unless an event e is causally overdetermined it cannot have more than one sufficient cause.

    Cases of overdetermination: two bullets hitting a victim; a short circuit and a lightning strike both causing a house fire.

  5. Here is the argument:
    1. Suppose that a mental event m causes a physical event p.
    2. According to the closure principle, there is a physical event p* that is a sufficient cause of p.
    3. Now, either m = p* or m ≠ p*.
    4. If m = p* then this is actually a case of physical-to-physical causation.
    5. If m ≠ p* then we have a case of causal overdetermination.
  6. I deliberatley left the argument a bit dodgy - how should we tidy it up?

The supervenience argument

  1. There is an argument, the supervenience argument, that there is no mental-to-mental causation.
  2. Back at the start of the course we considered the principle of mind-body supervenience:

    For all x and m: if m is a mental property and x has m then there is a p (a supervenience base for m) such that: p is a physical property and x has p and necessarily: for all y: if y has p then y has m.

    Example: pain.

  3. This principle poses a problem for mental-to-mental causation. Here is the supervenience argument:
    1. Suppose that an event e1 of mental kind m1 in a subject s caused an event e2 of mental kind m2 in s.
    2. So s has the mental property of being the subject of an event of kind m2.
    3. According to mind-body supervenience, there is a physical property p2 such that s has p2 and p2 is a supervenience base for m2.
    4. But now consider the event of s's instantiating p2 (call this e3). Isn't this event really the cause of e2? After all, it is not possible for this event to occur without e2 occurring: it is not possible for s to instantiate p2 without instantiating m2.
    5. So it seems that e1 is not really the cause of e2.
    6. So mental-to-mental causation is not possible.
  4. A possible response: Say that e1 caused e2 by first causing e3. One might appeal here to a more general principle: to causally affect a supervenient property one must causally affect its supervenience base properties (example: art).

    But this response relies on the possibility of mental-to-physical causation, and according to the exclusion argument mental-to-physical causation is not possible.

  5. Another possible response: Say that e1 = e3. That would mean that any mental event that causes a mental event is itself a physical event.

Contents 'aint in the head

  1. We are inclined to think that the contents of our beliefs make a causal difference. Why did I run away? Because I thought that I saw a crocodile. Had I thought that I'd seen a puppy I wouldn't have run away.
  2. But here is an argument against this idea:
    1. Ultimately it is the state of my brain that makes a causal difference.
    2. But the contents of my beliefs do not determine the state of my brain. (Why not? Putnam's Twin-Earth examples.)
    3. So the contents of my beliefs do not make a casual difference.
  3. What should we make of this argument?