The poet's high and passionate argument must be sought elsewhere, and precisely in his expression of his convictions about the world. And here, on the poet's word and the evidence of our search, we shall find phantasmagoria, ghostly symbols of a truth which cannot be otherwise conveyed, at least by Mr Yeats. To this, in itself, we make no demur. The poet, if he is a true poet, is driven to approach the highest reality he can apprehend. He cannot transcribe it simply because he does not possess the necessary apparatus of knowledge, and because if he did possess it his passion would flag. It is not often that Spinoza can disengage himself to write as he does at the beginning of the third book of the Ethics, nor could Lucretius often kindle so great a fire in his soul as that which made his material incandescent in _Æneadum genetrix_. Therefore the poet turns to myth as a foundation upon which he can explicate his imagination. He may take his myth from legend or familiar history, or he may create one for himself anew, but the function it fulfils is always the same. It supplies the elements with which he can build the structure of his parable, upon which he can make it elaborate enough to convey the multitudinous reactions of his soul to the world. But between myths and phantasmagoria there is a great gulf. The structural possibilities of the myth depend upon its intelligibility. The child knows upon what drama, played in what world, the curtain will rise when he hears the trumpet-note: 'Of man's first disobedience....' And, even when the poet turns from legend and history to create his own myth, he must make one whose validity is visible, if he is not to be condemned to the sterility of a coterie. The lawless and fantastic shapes of his own imagination need, even for their own perfect embodiment, the discipline of the common perception. The phantoms of the individual brain, left to their own waywardness, lose all solidity and become like primary forms of life, instead of the penultimate forms they should be. For the poet himself must move securely among his visions; they must be not less certain and steadfast than men are. To anchor them he needs intelligible myth. Nothing less than a supremely great genius can save him if he ventures into the vast without a landmark visible to other eyes than his own. Blake had a supremely great genius and was saved in part. The masculine vigour of his passion gave stability to the figures of his imagination. They are heroes because they are made to speak like heroes. Even in Blake's most recondite work there is always the moment when the clouds are parted and we recognise the austere and awful countenances of gods. The phantasmagoria of the dreamer have been mastered by the sheer creative will of the poet. Like Jacob, he wrestled until the going down of the sun with his angel and would not let him go.