This appears from the nature of his argument against the Utilitarians. In his time, this doctrine was associated with the names of Hartley, Tucker, Godwin, and especially Paley. He scarcely refers to Bentham.[194] Paley is the recognised anvil for the opposite school. Now he agrees, as I have said, with Paley's view of natural theology and entirely accepts therefore the theory of 'final causes.' The same theory becomes prominent in his ethical teaching. We may perhaps say that Stewart's view is in substance an inverted Utilitarianism. It may be best illustrated by an argument familiar in another application. Paley and his opponents might agree that the various instincts of an animal are so constituted that in point of fact they contribute to his preservation and his happiness. But from one point of view this appears to be simply to say that the conditions of existence necessitate a certain harmony, and that the harmony is therefore to be a consequence of his self-preservation. From the opposite point of view, which Stewart accepts, it appears that the self-preservation is the consequence of a pre-established harmony, which has been divinely appointed in order that he may live. Stewart, in short, is a 'teleologist' of the Paley variety. Psychology proves the existence of design in the moral world, as anatomy or physiology proves it in the physical.
Stewart therefore fully agrees that virtue generally produces happiness. If it be true (a doctrine, he thinks, beyond our competence to decide) that 'the sole principle of action in the Deity' is benevolence, it may be that he has commanded us to be virtuous because he sees virtue to be useful. In this case utility may be the final cause of morality; and the fact that virtue has this tendency gives the plausibility to utilitarian systems.[195] But the key to the difficulty is the distinction between 'final' and 'efficient' causes; for the efficient cause of morality is not the desire for happiness, but a primitive and simple instinct, namely, the moral faculty.
Thus he rejects Paley's notorious doctrine that virtue differs from prudence only in regarding the consequences in another world instead of consequences in this.[196] Reward and punishment 'presuppose the notions of right and wrong' and cannot be the source of those notions. The favourite doctrine of association, by which the Utilitarians explained unselfishness, is only admissible as accounting for modifications, such as are due to education and example, but 'presupposes the existence of certain principles which are common to all mankind.' The evidence of such principles is established by a long and discursive psychological discussion. It is enough to say that he admits two rational principles, 'self-love' and the 'moral faculty,' the coincidence of which is learned only by experience. The moral faculty reveals simple 'ideas' of right and wrong, which are incapable of any further analysis. But besides these, there is a hierarchy of other instincts or desires, which he calls 'implanted' because 'for aught we know' they may be of 'arbitrary appointment.'[197] Resentment, for example, is an implanted instinct, of which the 'final cause' is to defend us against 'sudden violence.'[198] Stewart's analysis is easygoing and suggests more problems than it solves. The general position, however, is clear enough, and not, I think, without much real force as against the Paley form of utilitarianism.