Just about everyone accepts that the mind interacts with the brain. Or, more technically, “some mental events interact causally with physical events”. Davidson gives a very concrete example of this:
Mental Events: perceivings, notings, calculations, judgements, decisions, intentional actions, changes of belief.
Physical Event(s): the sinking of the Bismarck.
The mental events above caused the physical event(s) below.
If there are causal events between the mind and the body, then, Davidson argues, these causal events must instantiate the kind of physical laws found in every other part of the universe. To use Davidson own words:
“…events related as cause and effect fall under strict deterministic laws.”
We think that this is the case simply because it's the case everywhere else in the universe (whether the cause and effect of a struck match lighting or a ball rolling along the ground).
The “third principle”, as Davidson calls it, tells us something that's not well-known outside the philosophy of mind. That is, that
“there are no strict deterministic laws on the basis of which mental events can be predicted and explained”.
This basically means that we can never really know, for certain, what a mind or a person (with a mind) will do next. If we strike a match in the right conditions, we know what will happen: it will light. Though put a mind or a person in a given situation, and we can't forecast precisely how he/she will act. We can, however, offer probabilistic forecasts of that mind’s behaviour; though this would be a forecast determined by past behaviours rather than the nature of the mind or the workings of the brain.
Because Davidson believes in what he calls “the anomalism of the mental” (i.e., that there aren't strict deterministic laws with which we can forecast, predict or explain mental events), then the Identity Theorist has a problem because he believes that the mental and the physical are identical. That must mean that there must be such laws for mental events.
Let’s be clear what the identity theorist believes. He believes that, for example, a particular pain is identical to a particular brain state. They're literally numerically identical.
Anomalous monism (the position advanced by Davidson) is still materialistic; despite the special position it gives to mental events. The anomalous monist believes that all events are physical. So why aren’t mental events subsumable under scientific laws? Well, for a start, the monist believes that “mental phenomena [can’t] be given purely physical explanations”. How does the monist account for this anomaly?
Firstly, although the mental and the physical aren't identical, there is a very close relation between the two. Mental phenomena depend or supervene on physical phenomena. And the supervenience thesis is both strong and, according to some, thoroughly physicalistic.
Let’s explain this close relation between mental events and physical events.
If two events are alike in all physical respects, then they'll be alike in all mental respects (despite the fact that they're not identical). To put the same position somewhat differently. Two objects can’t alter in some mental respect without altering in some physical respect.
To end this paragraph I will say a little on the monist’s position on reductionism (which is very important in the philosophy of mind), vis-à-vis the relation between mind and matter. As Davidson puts it:
“Dependence or supervenience of this kind does not entail reducibility through law or definition…”
Monism isn't a reductive physicalist position. The mind can’t be reduced to the brain without remainder. So supervenience doesn't entail psychophysical laws, which is Davidson’s original point.
Again, Davidson goes into the reasons why we can’t use physical predicates to describe or explain mental events. Despite his physicalism, he says that no physical predicate has the “same extension as a mental predicate”. So he seems to be saying that the physical and the mental are ontologically identical (hence the monism); though descriptively (or conceptually) non-identical. At a prima facie level, this seems to be a very hard position to defend: that is, ontological monism alongside conceptual dualism.
Davidson, to defend his case, goes into the long tradition of naturalistic attempts to define the mental (or supposedly non-physical) in terms of the physical. (A few decades ago, behaviourists tried to define or describe the mind - or the mental - in terms of observable physical behaviour.) He also thinks that naturalism in ethics failed, as well as instrumentalism and operationalism in the sciences, the causal theory of meaning in semantics and, finally, phenomenalism in epistemology. All these attempts at “definitional reductionism [were] conspicuously inadequate”, according to Davidson. So we can say that he's a realist about the mind or the mental (as well as about ethical terms or concepts) and also about the physical object posits of science and, finally, meaning as something non-reducible to the physical.
Now Davidson becomes slightly more technical and goes into detail about the anomalism of the mental. We can say that m is a mental event and p is a physical event. If m caused p, then “under some description m and p must instantiate a strict law”. Though this law must be physical because there are only physical laws. But “if m falls under a physical law, it [must have] a physical description”. That is to say that m must be a physical event. This in turn means that in order for m to be subsumed by laws, it must be described in the language of p. Davidson now says something that, prima facie, seems contradictory:
“So every mental event that is causally related to a physical event is a physical event.”
This appears to be saying that the mental is physical; or that the mental is both, well, mental and physical. But hasn’t Davidson been arguing against the mental’s subsuming under the physical (the “anomalism of the mental”)?
There's an idée fix running throughout all of this. It boils down to one thing: the necessity or possibility of human freedom. The explanation - or perhaps the guaranteeing of - free will could be said to be Davidson’s primary aim in his paper ‘Mental Events’. Despite the fact that earlier on he talks about “the efficacy of thought and purpose in the material world, and their freedom from law”, it's strange that he's only explicit on this matter at the very end of this paper. This is what he says:
“The anomalism of the mental is thus a necessary condition for viewing action as autonomous.”
To put that another way: we can say that the mind’s freedom from physical causation is necessary in order to secure us freedom (that is, free will). But which came first with Davidson? Did the arguments about the "anomalism of the mental" lead to his views about human freedom? Or did his pre-existing views about human freedom lead him to his arguments about the anomalism of the mental? Analytic philosophers, on the whole, would say that whether or not the chicken or the egg came first doesn’t really matter. If the arguments are valid and sound, then they're, well, valid and sound.
In any case, my argument that his faith in human freedom pre-dated his new philosophical defences of human freedom becomes a little stronger when bearing in mind his references to Kant (who, of course, undertook a similar enterprise).
In the last paragraph, Davidson pays homage to Kant by quoting, in full, a passage from Kant’s Fundamental Principles. This is the passage:
“'…we think of man in a different sense and relation when we call him free, and when we regard him as subject to the laws of nature…It must therefore show that not only can both of these very well coexist, but that both must be thought as necessarily united in the same subject.’”
Kant, even more clearly and categorically than Davidson, expresses the raison d’etre of Davidson’s – and Kant’s - enterprise: the securing of human freedom.
1 Davidson’s anomalous monism is as much an argument against psychological determinism as it is about anything else. The mental doesn't "fall under strict laws”. And this “is a necessary condition for viewing action as autonomous”. In the Kantian scheme also, the mental is free from causal law. It is a noumenon. The physical phenomenon is “subject to the laws of nature”. This is why there can't be psychophysical laws in Davidson’s scheme. The mental must therefore be outside nature.
Though if there are no laws of the mental, then perhaps events and happenings must be arbitrary or random in the mental domain. Mental acts must occur ex nihilo. Kant solved this problem by the supposition of non-natural transcendental laws which couldn't be proved to exist or even be known in any way. Davidson, in this paper, doesn't mention this problem.
In Spinoza’s fashion, Davidson claims that we can look at the mental qua mental and also the mental qua physical. m-descriptions can't be reduced down to p-descriptions. And, therefore, p-descriptions can't be lifted up to m-descriptions. Though if Davidson is a monist, m and p are the same “substance”. Therefore m = p. However, Davidson doesn’t appear to accept the ‘identity theory’. One can now ask: Can one be an ontological monist of mind and not be an identity theorist?