Thus libertarian free will has to disappear from their belief.
If the attack is to be finally repulsed it will be imperatively necessary for the libertarian to maintain that no full explanation of the physical universe can ever gain assent which does not take account of the reality and influence within the material world of human power of initiative and freedom.
That doctrine, if it is to possess cogency as a proof of the impossibility of the libertarian position, must assume that the amount of energy sufficient to account for physical and psychical changes is constant and invariable in quantity, an assumption which no scientific investigator is competent to prove.
Hedonistic psychology denied the libertarian hypothesis, but it denied also the absoluteness and intuitive character of moral obligation, and attached no validity to the ordinary interpretation of terms like "ought" and duty.
On the contrary, a belief that conduct necessarily results upon the presence of certain motives, and that upon the application of certain incentives, whether of pain or pleasure, upon the presence of certain stimuli whether in the shape of rewards or punishments, actions of a certain character will necessarily ensue, would seem to vindicate the rationality of ordinary penal legislation, if its aim be deterrent or reformatory, to a far greater extent than is possible upon the libertarian hypothesis.
The determinist equally with the libertarian moral philosopher can give an account of morality possessing internal coherence and a certain degree of verisimilitude.
Meanwhile the scientific onslaught upon the libertarian position has been directed from two chief quarters.
And the libertarian critic had before him a comparatively easy task when he exhibited the complete interdependence of character and environment, or rather the impossibility of treating either as definite and fixed factors in a process explicable by the use of ordinary scientific categories.
And the libertarian, by his arguments showing that appeal must be made to an act of will or of the self in the explanation of the phenomena of choice, does nothing directly to disprove the truth of such a contention.
Moreover, the belief that the justice of punishment depends upon the responsibility of the criminal for his past offences and the admission of the moral consciousness that his previous wrong-doing was freely chosen carries with it, so it is argued, consequences which the libertarian moralist might be willing to accept with reluctance.
For whatever may have been the character of the individual in the past, it is possible upon the libertarian view that by the exercise of his freedom he has brought about in himself a complete change of character: he may be now the exact opposite in character of what he was then.
While if the deterrent and reformatory theories alone provide a rational end for punishment to aim at then the libertarian hypothesis pushed to its extreme conclusion must make all punishments equally useless.
But whatever be the nature of the end chosen the libertarian is not concerned to deny that it must possess a fixed determinate character.
But the real strength of the libertarian position is to be found in the fact that consciousness is capable of distinguishing ends at all.
And there is much that is anticipatory of modern libertarian views in the psychological argument by which Carneades attempted at once to avoid the Epicurean identification of will with chance, and to prove the rationality of choice, undetermined by any external or antecedent necessity, as an explanation of human actions Xxviii.
But, as has been already suggested, the libertarian argument by no means necessarily leads to such extreme conclusions.