There are many men concerning whom it is certain that very little is known, and other men concerning whom it is certain that a great deal is known
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

““Poverty in a democracy is as much to be preferred to what is called prosperity under despots as freedom is to slavery,” he says. * It ended in 404 B.C. with the complete overthrow of Athens. Part II. Socrates, Plato, and Aristotle CHAPTER XI Socrates SOCRATES is a very difficult subject for the historian. There are many men concerning whom it is certain that very little is known, and other men concerning whom it is certain that a great deal is known; but in the case of Socrates the uncertainty is as to whether we know very little or a great deal. He was undoubtedly an Athenian citizen of moderate means, who spent his time in disputation, and taught philosophy to the young, but not for money, like the Sophists.” source