Preys on itself, and is destroyed by thought;
Constant attention wears the active mind,
Blots out her powers, and leaves a blank behind.”
Intense occupation of mind to any particular branch of study, often brings the mind on the verge of madness. “Since the ‘Essay on Truth’ was printed in quarto,” says Dr. Beattie, “I have never dared to read it over. I durst not even read the sheets to see whether there were any errors in the print, and was obliged to get a friend to do that office for me. These studies came, in time, to have dreadful effects upon my nervous system; and I cannot read what I then wrote without some degree of horror, because it recalls to my mind the horrors that I have sometimes felt after passing a long evening in these severe studies.”
Boerrhave has related of himself that, having imprudently indulged in intense thought on a particular subject, he did not close his eyes for six weeks afterwards.
Spinello, having painted the fall of the rebellious angels, had so strongly imagined the illusion, and more particularly the terrible features of Lucifer, that he was himself struck with such horror as to have been long afflicted with the presence of the demon to which his genius had given birth. Swedenburg saw a terrestrial heaven in the glittering streets of his New Jerusalem.
Malbranche declared he heard the voice of God distinctly within him. Pascal often was seen to rush suddenly from his chair at the appearance of a fiery gulf by his side. Luther maintained that during his confinement the devil used to visit him.
Hudibras says—
“Did not the devil appear to Martin
Luther, in Germany, for certain?”