In the midst of his many interests and activities, Crookes was filled from his youth with a longing to find by empirical means the bridge leading from the world of physical effects to that of superphysical causes. He himself tells how this longing was awakened in him by the loss of a much-beloved brother. Before the dead body he came to the question, which thereafter was never to leave him, whether there was a land where the human individuality continues after it has laid aside its bodily sheath, and how that land was to be found. Seeing that scientific research was the instrument which modern man had forged to penetrate through the veil of external phenomena to the causes producing them, it was natural for Crookes to turn to it in seeking the way from the one world into the other.