A symbol is indeed the only possible expression of some invisible essence, a transparent lamp about a spiritual flame; while allegory is one of many possible representations of an embodied thing, or familiar principle, and belongs to fancy and not to imagination: the one is a revelation, the other an amusement.
William Butler YeatsThough I am old with wandering Through hollow lands and hilly lands, I will find out where she has gone, And kiss her lips and take her hands; And walk among long dappled grass, And pluck till time and times are done The silver apples of the moon, The golden apples of the sun.
William Butler Yeats