Demoniac possession is mythical; but the faculty of being possessed,
more or less completely, by an idea is probably the fundamental
condition of what is called genius, whether it show itself in the saint,
the artist, or the man of science. One calls it faith, another calls it
inspiration, a third calls it insight; but the "intending of the mind,"
to borrow Newton's well-known phrase, the concentration of all the rays
of intellectual energy on some one point, until it glows and colours the
whole cast of thought with its peculiar light, is common to all.