Those Determinists, of course, who do not admit the existence of a 'mind' as distinct from a 'body' at all, or again, those who, while admitting the existence of mind, deny that it has any efficacy in bringing about the changes which comprise human behaviour, will not be affected by the questionable character of the analogy of mind with matter. The analogy, for them, is of one set of material processes with another set. They do not bring 'mind' into the argument. But in adopting this position they do not strengthen, but immeasurably weaken, the demonstrable case for determinism in human behaviour. For it is not now permitted to them to take any account of the undoubtedly impressive evidence for causal continuity referred to in the preceding paragraph, viz. that furnished by the relative constancy observable in the relation between 'character' and 'conduct.' The Behaviouristic Determinist is only entitled to assert intelligible continuity if he can show constant relations between the material processes of the body and the material processes which constitute conduct. It is safe to say that he is very much further off from his goal than the 'spiritual' Determinist is from his. A beginning has been made, let us admit, with the 'conditioned reflex' and its allies. But it is the merest beginning. So far as the present writer has been able to discern, explanation by the 'conditioned reflex' has not yet extended, in actual practice, beyond certain extremely simple types of experience, in respect of which the defender of freedom would not be in the least perturbed at having to admit that he is essentially 'inactive.' The speculative jump required to extend the principle to cover the whole gamut of human behaviour may fairly be described as prodigious.
(2) Even if the Determinist does succeed in assuring himself that the observed facts demand a deterministic explanation, nevertheless this assurance will not of itself be effectual in silencing the contrary testimony of his practical consciousness. And since the practical consciousness is as integral a part of himself as the theoretical, his soul will become the seat of an unresolved dualism which, to him as a philosopher, cannot be other than embarrassing. With one side of his nature he will find himself denying freedom, while with another side asserting it. In such a situation it is impossible that he should be confident of the validity of either pronouncement, or expect others, similarly circumstanced, to be persuaded by his arguments. It will behove him, therefore, if he is to attain to a satisfying Determinism, to expose the illusoriness of the common testimony of the practical consciousness - an end which can only be achieved if, by an analysis of the experience which underlies it, he is able to show that what seems to be a spontaneous and necessary interpretation is really an understandable misinterpretation, the confusion in which, once brought to light, we may guard ourselves from repeating. Only by a demonstration along these lines could the dualism be resolved in favour of Determinism.
It is for the Determinist, then, a matter of vital importance to 'explain away' the 'practical' certitude of freedom, to show that the experience underlying it does not really compel the affirmation which it seems to compel. And it is even more vital for the Libertarian to repel such attempts. For if he cannot maintain his case here, there is nothing else, we repeat, to which he can appeal for positive support. In fairness to the Libertarian, however, it must again be emphasised that his obligation is rather to rebut contrary arguments than to initiate a positive argument. The onus of proof lies upon the Determinist. For it cannot be denied that everyone knows what is meant when we speak of putting forth an 'effort of will' and acting against what is felt to be the 'line of least resistance,' and it is certain that the universal interpretation which such experiences evoke, apart from theory, is 'libertarian.' If the Determinisms arguments do not succeed in disturbing the natural interpretation, the Libertarian position may fairly be said to stand: always providing, however, that the Libertarian is able to show also that the freedom which he asserts is incompatible neither with observed facts nor with any well-authenticated metaphysical postulate.