Thursday, June 9, 2011

Mind-Body Physicalism (Part One): The Argument from Past Explanatory Success

Since I did a whole series on the basic arguments for and against substance dualism, I thought it might be nice to do a symmetrical series on the basic arguments for and against mind-body physicalism. I’m sure some of my readers will like this too - they suggested as much in the comments section. As with my series on substance dualism, William Jaworski’s book Philosophy of Mind: a Comprehensive Introduction will be the source material.

It’s only right that I warn you at the outset: Although the motivation for this series is to serve the interests of symmetry, there are differences between the treatment of the two positions that will make this series on physicalism far less satisfactory than the one on substance dualism. Primarily, this is due to the fact that there has been a lot more theoretical refinement of physicalism over recent years. Indeed, such is the volume of theoretical refinements that Jaworski spends four whole chapters going over them.

I don’t wish to follow each and every refinement here - there’s no sense in producing the book as a whole - so instead I’ll just cover one basic argument for physicalism (the argument from past scientific success) and three objections to physicalism (Hempel’s dilemma, the knowledge argument, and the problem of inverted qualia). These three objections provide the springboard for the further refinements mentioned above. Some of these are impressive and the arguments in their favour can be quite compelling, but if you’re interested in these then I recommend getting a hold of Jaworski’s book (this is the last recommendation for a while - I don’t want to end up as Jaworski’s personal promoter).

1. The Argument from Past Explanatory Success
Physicalists come in many flavours, but they usually share one basic commitment: the commitment to the fundamentality of the physical sciences. That is to say, they all tend to believe that whatever reality ultimately consists in will only be properly described using the language of physics. Furthermore, that which is properly described using the language of physics is called “physical”. So since the mind is part of reality, it would seem to follow that mind must ultimately be physical.

Clearly this commitment to physics is in want of justification. This is where the argument from past explanatory success comes into play. Before discussing that argument it’s worth making something clear: there are other arguments in favour of physicalism in general and also in favour of particular forms of physicalism. Indeed, we encountered one such argument - the argument from the problem of interaction - when looking at substance dualism. But even that argument would seem to trace its authority back to the explanatory success of physics. Anyway, the argument itself takes the following form:

  • (1) If explanations of type A have, in the past, been superior to explanations of type B (with respect to a broad range of subject matters), then explanations of type A are likely to be superior to explanations of type B with respect to other subject matters.
  • (2) Physical explanations have, in the past, been superior to non-physical explanations with respect to a broad range of subject matters.
  • (3) Mind-body relations are a subject matter in want of an explanation.
  • (4) Therefore, physical explanations are likely to be superior to non-physical explanations with respect to mind-body relations.

Now this might look a little bit strange. For one thing, it doesn’t appear in this form in Jaworski’s text. He presents the argument as a straightforward {“Physical explanations have been superior to non-physical explanations in the past” → “Therefore, physical explanations are likely to best with respect to mind-body relations”} inference. His version makes the inductive gap between the premise and the conclusion transparent. I’ve tried to plug this gap by introducing an explicit inductive principle in the shape of premise (1). But this does not change the overall strength of the argument.

And this is the critical point. Inductive arguments of this sort cannot provide decisive reasons in favour of a particular conclusion. They can only provide probabilistic reasons for supporting a conclusion. The probabilities in question might be very high, but they are probabilistic nonetheless. Does this make things easier for the critic of physicalism? Not necessarily. We each of us rely on inductive principles, so the proponent of an alternative theory should be reluctant to dismiss the argument solely because it is inductive in nature. Instead, they should prefer to provide some good reason for thinking induction is unwarranted in this particular instance. Which brings us to….

2. Supporting the Argument
The key to the argument from past explanatory success is the support given to premise (2). If many impressive examples of successful physical explanations can be given, then dualists will have their work cut out. To block the induction from these case studies, they will need to show that mind-body relations are completely disanalogous to them. That’s certainly not impossible but it must be done nonetheless.

So what examples can be adduced in support of premise (2)? Jaworski offers four. Now, I’m not a historian of science so I can’t really vouch for the accuracy of each of them. They sound plausible to me but, for instance, I have no idea if people ever really did explain magnetism by appeal to non-physical spirits. Also, I would presume that the success of physicalistic explanations in each of these domains is determined by following the rules of inference to best explanation or some probabilistic alternative (Bayesian or Likelihoodist). In other words, physicalist explanations win against competitor explanations because they are simpler, afford us greater predictive and manipulative powers, confer a higher probability on the data and so on ( see this series for more ).

Anyway, the four examples are:

  • (2.1) Magnetism : At one point in time people tried to explain magnetic by positing the presence of nonphysical spirits in magnetised objects. A physicalistic explanation of magnetism in terms of the electromagnetic force proved far more successful.
  • (2.2) Planetary Motion : At one point people thought non-physical intelligences (gods) could account for the orbital movements of the planets. This was replaced by a far more successful physicalistic explanation of those movements by reference (initially) to Newtonian laws of gravity and (eventually) to the warping of spacetime.
  • (2.3) Life : People once thought that the only thing capable of explaining the nature and behaviour of living things was by positing the existence, in them, of non-physical vital spirits. This has now been replaced by a far more successful explanation of life in terms of mechanical metabolic and reproductive processes.
  • (2.4) Mental Illness Abnormal human behaviour was once explained by reference to possession by non-physical beings. Now many (if not all) such abnormalities can be explained by reference to tissue pathologies or alterations in the electrical and chemical balance of the brain.

We can plug these four examples into the argument and then map it out as follows.

Now as has been stressed already this argument is far from watertight. We’ll consider the various problems with it, and with physicalism as a whole, over the remainder of this series.


  1. "will make this series on physicalism far less satisfactory than the one on physicalism"

    ITYM on "dualism" at the end there?