Chiefly, however, determinism is self-stultifying. If my mental processes are totally determined, I am totally determined either to accept or to reject determinism. But if the sole reason for my believing or not believing X is that I am causally determined to believe it I have no ground for holding that my judgment is true or false. J. R. Lucas has put the point cogently with reference to Marxist and Freudian forms of determinism thus. 'The Marxist who says that all ideologies have no independent validity and merely reflect the class interests of those who hold them can be told that in that case his Marxist views merely express the economic interests of his class, and have no more claim to be judged true or valid than any toher view. So too the Freudian, if he makes out that everybody else's philosophy is merely the consequence of childhood experiences, is, by parity of reasoning, revealing merely his delayed response to what happened to him when he was a child.' Lucas then makes the same point with regard to a person who maintains, more generally, that our behaviour is totally determined by heredity and environment. 'If what he says is true, he says it merely as the result of his heredity and environment, and of nothing else. He does not hold his determinist views because they are true, but because he has such-and-such a genetic make-up, and has received such-and-such stimuli; that is, not because the structure of the universe is such-and-such but only because the configuration of only one part of the universe, together with the structure of the determinist's brain, is such as to produce that result.'
The exact force of this criticism is sometimes missed. Certainly on deterministic premisses determinism may be true. But we should not have any grounds for affirming that it is true or therefore for knowing that it is so. In order to obtain these grounds we must be free from all determining factors in order to assess the evidence according to its own worth. This principle applies to the assessment of all truth-claims (including those of Christianity). Freedom from determining factors is therefore required in the cognitive as much as in the moral sphere.
Huw Parri Owen
Christian Theism: A Study in Its Basic Principles
(quoting J. R. Lucas, The Freedom of the Will)