One difference there is between scientific and imaginative truth,—­a difference in the mode of statement.  Science and also philosophy formulate truth and end in the formula; literature, as the saying is, clothes truth in a tale.  Imagination is brought in, and by its aid the mind projects a world of its own, whose principle of being is that it reembodies general or abstract truth and presents it concretely to the eye of the mind, and in some arts gives it physical form.  So, to draw an example from science itself, when Leverrier projected in imagination the planet Uranus, he incarnated in matter a whole group of universal qualities and relations, all that go to make up a world, and in so doing he created as the poet creates; there was as much of truth, too, in his imagined world before he found the actual planet as there was of reality in the planet itself after it swam into his ken.  This creation of the concrete world of art is the joint act of the imagination and the reason working in unison; and hence the faculty to which this act is ascribed is sometimes called the creative reason, or shaping power of the mind, in distinction from the scientific intellect which merely knows.  The term is intended to convey at once the double phase, under one aspect of which the reason controls imagination, and under the other aspect the imagination formulates the reason; it is meant to free the idea, on the one hand, from that suggestion of abstraction implied by the reason, and to disembarrass it, on the other, of any connection with the irrational fancy; for the world of art so conceived is necessarily both concrete, correspondent to the realities of experience, and truthful, subject to the laws of the universe; it cannot contain the impossible, it cannot amalgamate the actual with the unreal, it cannot in any way lie and retain its own nature.  The use of this rational imagination is not confined to the world of art.  It is only by its aid that we build up the horizons of our earthly life and fill them with objects and events beyond the reach of our senses.  To it we are indebted for our knowledge of the greater part of others’ lives, for our idea of the earth’s surface and the doings of foreign nations, of all past history and its scene, and the events of primaeval nature which were even before man was.  So far as we realize the world at all beyond the limit of our private experience of it, we do so by the power of the imagination acting on the lines of reason.  It fills space and time for us through all their compass.  Nor is it less operative in the practical pursuits of men.  The scientist lights his way with it; the statesman forecasts reform by it, building in thought the state which he afterward realizes in fact; the entire future lives to us—­and it is the most important part of life—­only by its incantation.  The poet acts no otherwise in employing it than the inventor and the speculator even, save that he uses it for the ends of reason instead of