here 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.

Swedenborg's imaginative mind seems to have fully felt the charm of this
interesting subject. It was, indeed, because of the charm which he found
in it, that he was readily persuaded into the belief that knowledge had
been supernaturally communicated to him respecting it. 'Because I had a
desire,' he says, 'to know if there are other earths, and to learn their
nature and the character of their inhabitants, it was granted me by the
Lord to converse and have intercourse with spirits and angels who had
come from other earths