Shakespeare's sonnet

How plainly here the poet speaks! In the enormous plenitude of his conceptions which have not as yet found a human sphere to vent themselves, the thought occupies him that his mind as well as his body will grow old, that the exuberance, or beauty, of his intellect, now gazed on with so much admiration, the youthful freshness of his intellectual powers, which now afford him such delight, will gradually decay, some day cease to …

…first arises from a social morality dependent on others_ response, in which one acts so as to avoid shame, or receive praise, or make excuse. The social morality of the body of the poem, however, is displaced in the closing couplet by an appeal to individual pleasure: the reward for reproducing and the source of self-worth is now narcissistic (warm blood, new self) rather than social, and, if not purely intrinsic, at least entirely self-referential.