What is often called free will, or freedom, I prefer to call intention.
Firstly, note that belief in the reality of intention does not violate natural science. It has no place within natural science, but it lives perfectly at peace with it.
"Prevision will never foretell, even if the effort be completely predestinate, the actual way in which each individual emergency is resolved. Psychology will be Psychology, and Science Science, as much as ever (as much and no more) in this world, whether free-will be true in it or not. Science, however, must be constantly reminded that her purposes are not the only purposes, and that the order of uniform causation which she has use for, and is therefore right in postulating, may be enveloped in a wider order, on which she has no claims at all. ... The operation of free effort, if it existed, could only be to hold some one ideal object, or part of an object, a little longer or a little more intensely before the mind. Amongst the alternatives which present themselves as genuine possibles, it would thus make one effective. And although such quickening of one idea might be morally and historically momentous, yet, if considered dynamically, it would be an operation amongst those physiological infinitesimals which calculation must forever neglect."
William James, Principles of Psychology (1890), Chapter 26.
Then to the positive case. The only airtight arguments are those (such as saying that all black cats are black) that cannot be contradicted without self-contradiction ("tautologies"). So on the present topic, which is about reality not merely about definitions, the case can never be "airtight", but if I am allowed the distinction I think I would call it "watertight".
The very fact that freedom is a problem for reason is itself a reason for believing that we are free. Many men have sensed this, but the argument is extremely difficult to articulate and assess.
John Lucas, The Freedom of the Will, Chapter 1.
Lucas' is the best attempt to tighten up the argument that I know of.
Firstly he develops some traditional arguments, such as:
Determinism cannot be true, because if it was, we should not take the determinists' arguments as being really arguments, but as being only conditioned reflexes. ... Reasoning, and hence truth, presupposes freedom just as much as deliberation and moral choice do.
John Lucas, The Freedom of the Will, Chapter 21. ("Determinism" is the view that everything that happens has already been fixed.)
Then he attempts something new. He claims that Godel's theorems imply that any mechanistic model of a man can be shown to be false, and that the only way to maintain that a man is a mechanism is to say that not all models are false even though every model one could propose would be false, a position which is not technically inconsistent (and therefore cannot be proved false by ordinary logic) but which would be regarded as bizarre by any ordinary folk able to understand it (and technically called omega-inconsistent). There is just one link in the chain of Lucas' reasoning that I am doubtful about, so I cannot quite endorse his thesis as the final answer to this problem, but I can find no trace of scholarly criticism of him on this point, so I suspect that he is probably right.
The one doubtful point is his claim, in Chapter 25, that:
"Assuming determinism, "there are only a finite numbers of circumstances ... that are discriminably different. For there are only a finite number of independent variables, and although ... these are thought to vary continuously, very small differences, at least in the environment, are not perceived by the human organism, and make no difference to its responses. We have therefore only a definite finite number ... of possible circumstances affecting a particular human being." So the number of possible beliefs for a given human is finite, and "the reasoning of any particular human being can be viewed as a logistic calculus". Call that calculus "L". Then there is a statement in L which is unprovable in L (so the agent cannot produce it as true) but which any rational being can see to be true (so the agent, being human hence rational, can see it). This is a contradiction, so the assumption was false."
Assuming continuously variable stimulus, I see no grounds to reject continuously variable response, and to me this point looks crucial. But I can find no trace of scholarly criticism of him on this point, so probably I am wrong.
In a sense we can "force" folk (or at least, folk with certain training) to acknowledge the force of logic, but not the force of reason.
We cannot make people see reason.
John Lucas, The Freedom of the Will, Chapter 28.
Finally Lucas explains that the Godelian argument is only a way of formalising the traditional ones.
It is inherent in our idea of a conscious mind that it can reflect upon itself and criticize its own performances, without thereby becoming different. Godel's theorem only enables us to express in mathematical terms what we have always known about a man's own awareness of himself. ... Our argument is thus, at bottom, one of conceptual analysis rather than mathematical discovery. ... Godel's theorem enables us to crystallize out our intuitive notions and intimations of freedom in such a way that we can be sure that they apply to any form of physical determinism. [It] enables us to formulate the objection we felt to the determinist's maintaining that what he said was true in spite of being determined, in a way which is not liable to the charge of meaninglessness that can be made against most self-referential arguments.
John Lucas, The Freedom of the Will, Chapter 29.
(Behaviourism) Here is a classic statement of a position that its author called "materialism", from the founder of Behaviourism.
"Life as a whole, from the simplest to the most complex organisms, including man, is a long series of equilibrations with the environment -- equilibrations which reach the highest degree of complexity. And the time will come, distant or not, when mathematical analysis based on natural science will express in majestic formulae of equation all these equilibrations, including, in the final analysis, itself."
Pavlov, Natural Science and the Brain, 1909.
I would love to know what he supposes the "majestic formula" expressing the above statement might look like. Interestingly he added the following; let materialists judge for themselves whether it coheres with the above statement, and if so, what kind of "formula" might express it.
"I do not deny psychology as a body of knowledge concerning the internal world of man. Even less am I inclined to negate anything which relates to the innermost and deepest strivings of the human spirit."
Pavlov, Natural Science and the Brain, 1909.
Back to Our Task as Humans.