Keats's poetical indifference to theories and principles was, however, in itself a theory and a principle--was the philosophy which has its foundation in poetic worship of nature. To the consistent pantheistic poet all forms, all shapes, all expressions of life on earth which engage the imagination, are precious, and all equally precious. Keats, as poet, recognises no truth of the kind that means improvement or exclusion; but he has an almost religious faith in imagination as the source of truth. In one of his letters he expresses himself thus:--"I am certain of nothing but of the holiness of the heart's affections, and the truth of Imagination. What the Imagination seizes as Beauty must be Truth, whether it existed before or not;--for I have the same idea of all our passions as of Love: they are all, in their sublime, creative of essential Beauty.... The Imagination may be compared to Adam's dream; he awoke and found it truth." He enlarges on the difference between this kind of truth and the truth arrived at by consecutive reasoning, and concludes with an exclamation which is a key to the whole of his poetry:--"However it may be, O for a life of sensations rather than of thoughts!" He led in great part a life of passive sensation, of pleasure and pain through the senses. "Take," says Masson, "a book of physiology and go over the so-called classes of sensations one by one--the sensations of the mere muscular states; the sensations connected with such vital processes as circulation, alimentation, respiration, and electrical intercommunication with surrounding bodies; the sensations of taste; those of odour; those of hearing; and those of sight--and Keats will be found to have been unusually endowed in them all." He had, for example, an extreme sensitiveness to the pleasures of the palate, and tried to heighten them by extraordinary stimulants. A friend tells us that he once saw Keats covering his tongue with cayenne pepper, that he might enjoy the delicious sensation of a draught of cold claret after it. "Talking of pleasure," he says himself in one of his letters, "this moment I was writing with one hand and with the other holding to my mouth a nectarine." It is therefore not surprising that imagery drawn from the domain of the sense of taste is of frequent occurrence in Keats's poetry. In his deservedly famous _Ode to Melancholy_ we are told that this goddess has her sovran shrine in the very temple of Delight-- "Though seen of none save him _whose strenuous tongue_ _Can burst Joy's grape against his palate fine!_" And in one of his last sonnets he characteristically mentions "the palate of my mind losing its gust" as an indication of approaching death.