a man very sure of himself, high-minded, indifferent to worldly success, believing that he is guided by a divine voice, and persuaded that clear thinking is the most important requisite for right, living.
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“For besides being happier than we are, they will be immortal, if what is said is true.... “The hour of departure has arrived, and we go our ways—I to die, and you to live. Which is better God only knows.” The Apology gives a clear picture of a man of a certain type: a man very sure of himself, high-minded, indifferent to worldly success, believing that he is guided by a divine voice, and persuaded that clear thinking is the most important requisite for right, living. Except in this last point, he resembles a Christian martyr or a Puritan. In the final passage, where he considers what happens after death, it is impossible not to feel that he firmly believes in immortality, and that his professed uncertainty is only assumed.” source