From a mistaken appreciation of the real process this would by few be called an effort of Imagination.  On the contrary some “wild hypothesis” would be lauded as imaginative in proportion as it departed from all suggestion of experience, i.e. real mental vision.  To have imagined that the feather rose owing to its “specific lightness,” and that the quill fell owing to its “heaviness,” would to many appear a more decided effort of the imaginative faculty.  Whereas it is no effort of that faculty at all; it is simply naming differently the facts it pretends to explain.  To imagine—–­to form an image—­we must have the numerous relations of things present to the mind, and see the objects in their actual order.  In this we are of course greatly aided by the mass of organised experience, which allows us rapidly to estimate the relations of gravity or affinity just as we remember that fire burns and that heated bodies expand.  But be the aid great or small, and the result victorious or disastrous, the imaginative process is always the same.

There is a slighter strain on the imagination of the poet, because of his greater freedom.  He is not, like the philosopher, limited to the things which are, or were.  His vision includes things which might be, and things which never were.  The philosopher is not entitled to assume that Nature sympathises with man; he must prove the fact to be so if he intend making any use of it ;—­we admit no deductions from unproved assumptions.  But the poet is at perfect liberty to assume this; and having done so, he paints what would be the manifestations of this sympathy.  The naturalist who should describe a hippogriff would incur the laughing scorn of Europe; but the poet feigns its existence, and all Europe is delighted when it rises with Astolfo in the air.  We never pause to ask the poet whether such an animal exists.  He has seen it, and we see it with his eyes.  Talking trees do not startle us in Virgil and Tennyson.  Puck and Titania, Hamlet and Falstaff, are as true for us as Luther and Napoleon so long as we are in the realm of Art.  We grant the poet a free privilege because he will use it only for our pleasure.  In Science pleasure is not an object, and we give no licence.

Philosophy and Art both render the invisible visible by imagination.  Where Sense observes two isolated objects, Imagination discloses two related objects.  This relation is the nexus visible.  We had not seen it before; it is apparent now.  Where we should only see a calamity the poet makes us see a tragedy.  Where we could only see a sunrise he enables us to see

“Day like a mighty river flowing in.”