1. Our usual mode of speaking of imagination, is to treat it as the opposite of all reality. When we say, 'that was merely an imagination,' we dismiss the topic as not worthy of another thought. For all ordinary purposes, this mode of speaking is correct enough; but let us ask, Why is imagination so weak?--why are its suggestions so evanescent? Simply because it is under the control of reason. But if the action of reason could be suspended, we should then see how great, and even formidable, is the imaginative power. It is the most untiring of all our mental faculties, refusing to be put to rest even during sleep: it can alter the influence of all external agents--for example, can either assist or prevent the effects of medicine--can make the world a prison-house to one man, and a paradise to another--can turn dwarfs into giants, and make various other metamorphoses more wonderful than any described by Ovid; nay, these are all insufficient examples of its power when left without control; for it can produce either health, or disease, or death! To give a familiar instance of the control under which it is generally compelled to act: You are walking home in the night-time, and some withered and broken old tree assumes, for a moment, the appearance of a giant about to make an attack upon you with an enormous club. You walk forward to confront the monster with perfect coolness. Why? Not because you are a Mr Greatheart, accustomed to deal with giants, but because, in fact, the illusion does not keep possession of your mind even for a moment. Imagination merely suggests the false image; but memory and reason, with a rapidity of action which cannot be described, instantly correct the mistake, and tell you it is only the old elm-tree; so that here, and in a thousand similar instances, there is really no sufficient time allowed for any display of the power of imagination.