Two facts in connection with mysticism are undeniable whatever it may be, and whatever part it is destined to play in the development of thought and of knowledge. In the first place, it is the leading characteristic of some of the greatest thinkers of the world--of the founders of the Eastern religions of Plato and Plotinus, of Eckhart and Bruno, of Spinoza, Goethe, and Hegel. Secondly, no one has ever been a lukewarm, an indifferent, or an unhappy mystic. If a man has this particular temperament, his mysticism is the very centre of his being: it is the flame which feeds his whole life; and he is intensely and supremely happy just so far as he is steeped in it. Mysticism is, in truth, a temper rather than a doctrine, an atmosphere rather than a system of philosophy. Various mystical thinkers have contributed fresh aspects of Truth as they saw her, for they have caught glimpses of her face at different angles, transfigured by diverse emotions, so that their testimony, and in some respects their views, are dissimilar to the point of contradiction. Wordsworth, for instance, gained his revelation of divinity through Nature, and through Nature alone; whereas to Blake "Nature was a hindrance," and Imagination the only reality. But all alike agree in one respect, in one passionate assertion, and this is that unity underlies diversity. This, their starting-point and their goal, is the basic fact of mysticism, which, in its widest sense, may be described as an attitude of mind founded upon an intuitive or experienced conviction of unity, of oneness, of alikeness in all things. From this source springs all mystical thought, and the mystic, of whatever age or country, would say in the words of Krishna-- There is true knowledge. Learn thou it is this: To see one changeless Life in all the Lives, And in the Separate, One Inseparable. _The Bhagavad-Gîtâ_, Book 18. This fundamental belief in unity leads naturally to the further belief that all things about us are but forms or manifestations of the one divine life, and that these phenomena are fleeting and impermanent, although the spirit which informs them is immortal and endures. In other words, it leads to the belief that "the Ideal is the only Real."