It indicates the fulness of Swedenborg's belief in this privilege that he did not hesitate to describe what the spirits taught him respecting matters which belong rather to science than to faith; though it must be admitted that probably he supposed there was small reason for believing that his statements could ever be tested by the results of scientific research. The objects to which his spiritual communications related were conveniently remote. I do not say this as desiring for one moment to suggest that he purposely selected those objects, and not others which might be more readily examined. He certainly believed in the reality of the communications he described. But possibly there is some law in things visionary, corresponding to the law of mental operation with regard to scientific theories; and as the mind theorises freely about a subject little understood, but cautiously where many facts have been ascertained, so probably exact knowledge of a subject prevents the operation of those illusions which are regarded as supernatural communications. It is in a dim light only that the active imagination pictures objects which do not really exist; in the clear light of day they can no longer be imagined. So it is with mental processes. Probably there is no subject more suitable in this sense for the visionary than that of life in other worlds. It has always had an attraction for imaginative minds, simply because it is enwrapped in so profound a mystery; and there has been little to restrain the fancy, because so little is certainly known of the physical condition of other worlds. Recently, indeed, a somewhat sudden and severe check has been placed on the liveliness of imagination which had enabled men formerly to picture to themselves the inhabitants of other orbs in space. Spectroscopic analysis and exact telescopic scrutiny will not permit some speculations to be entertained which formerly met with favour. Yet even now there has been but a slight change of scene and time. If men can no longer imagine inhabitants of one planet because it is too hot, or of another because it is too cold, of one body because it is too deeply immersed in vaporous masses, or of another because it has neither atmosphere nor water, we have only to speculate about the unseen worlds which circle round those other suns, the stars; or, instead of changing the region of space where we imagine worlds, we can look backward to the time when planets now cold and dead were warm with life, or forward to the distant future when planets now glowing with fiery heat shall have cooled down to a habitable condition.