Mackintosh, is infinitely superior to the pleasures to which it may lead. Could it become 'lasting and intense,' it would convert the heart into a heaven.[577] To love virtue, you must love it 'for its own sake.'[578] The delights of being virtuous (as he interprets the phrase) are greater than any delight from the consequences of virtue. And he holds up as a model Fletcher of Saltoun, who would 'lose his life to serve his country, but would not do a base thing to save it.'[579] How, then, is this view to be reconciled with the unreserved admission of 'utility' as the 'criterion' of right and wrong? One answer is that Mackintosh fully accepts Hartley's doctrine of association. He even criticises previous philosophers for not pushing it far enough. He says that association, instead of merely combining a 'thought' and a 'feeling,' 'forms them into a new compound, in which the properties of the component parts are no longer discoverable, and which may itself become a substantive principle of human virtue.'[580] The question of origin, therefore, is different from the question of nature. He follows Hartley in tracing the development of various desires, and in showing how the 'secondary desires' are gradually formed from the primitive by transference to different objects.[581] We must start from feelings which lie beneath any intellectual process, and thus the judgment of utility is from the first secondary. We arrive at the higher feelings which are 'as independent as if they were underived,'[582] and yet, as happiness has been involved at every stage as an end of each desire, it is no wonder that the ultimate result should be to make the general happiness the end. The coincidence, then, of the criterion with the end of the moral sentiments is 'not arbitrary,' but arises necessarily from 'the laws of human nature and the circumstances in which mankind are placed.'[583] Hence we reach the doctrine which 'has escaped Hartley as well as every other philosopher.'[584] That doctrine is that the moral faculty is one; it is compound, indeed, in its origin; but becomes an independent unit, which can no longer be resolved even in thought into its constituent elements.