“But the facts of Nature are to be discovered only by observation and experiment.” True. But how does the man of science come to think of his experiments? Does observation reach to the non-present, the possible, the yet unconceived? Even if it showed you the experiments which _ought_ to be made, will observation reveal to you the experiments which _might_ be made? And who can tell of which kind is the one that carries in its bosom the secret of the law you seek? We yield you your facts. The laws we claim for the prophetic imagination. “He hath set the world _in_ man’s heart,” not in his understanding. And the heart must open the door to the understanding. It is the far-seeing imagination which beholds what might be a form of things, and says to the intellect: “Try whether that may not be the form of these things;” which beholds or invents _a_ harmonious relation of parts and operations, and sends the intellect to find out whether that be not _the_ harmonious relation of them--that is, the law of the phenomenon it contemplates. Nay, the poetic relations themselves in the phenomenon may suggest to the imagination the law that rules its scientific life. Yea, more than this: we dare to claim for the true, childlike, humble imagination, such an inward oneness with the laws of the universe that it possesses in itself an insight into the very nature of things. Lord Bacon tells us that a prudent question is the half of knowledge. Whence comes this prudent question? we repeat. And we answer, From the imagination. It is the imagination that suggests in what direction to make the new inquiry--which, should it cast no immediate light on the answer sought, can yet hardly fail to be a step towards final discovery. Every experiment has its origin in hypothesis; without the scaffolding of hypothesis, the house of science could never arise. And the construction of any hypothesis whatever is the work of the imagination. The man who cannot invent will never discover. The imagination often gets a glimpse of the law itself long before it is or can be _ascertained_ to be a law. [Footnote: This paper was already written when, happening to mention the present subject to a mathematical friend, a lecturer at one of the universities, he gave us a corroborative instance. He had lately _guessed_ that a certain algebraic process could be shortened exceedingly if the method which his imagination suggested should prove to be a true one--that is, an algebraic law. He put it to the test of experiment--committed the verification, that is, into the hands of his intellect--and found the method true. It has since been accepted by the Royal Society.