Can we call great men truly great if they have said things we now know are not only false but even offensive? For example, Aristotle thought that some men are “naturally slaves,” and that women should be subjects to men. Heidegger was a Nazi supporter, Plato supported a closed society in which the few ruled with little or no restraint, Ptolemy thought the earth was at the center of a finite universe. And so on. Are these men still “great”? This is an interesting question and it was raised in a comic I read on a daily basis, believe it or not.

But the issue fails to focus on one central point: we need not worry about who said what; we need to focus on what was said. I realize that Curtler’s Second Law states that we should consider the source of comments in weighing their worth — in the case of complex national issues involving, say, the future of the planet where special interests are involved. But in general, we are prone to the ad hominem fallacy in our culture, where we reject an argument because of who put it forward. “Oh, that can’t be true, the man’s a liberal.” Or, “that is absurd; after all she is known to be a loose woman.” Or whatever. We forget that liberals (and even conservatives) and loose women can put forward excellent arguments. In the vast majority of cases the arguments stand or fall on their own feet. It matters not who put them forward.

Aristotle said many foolish things. And he was certainly wrong to ignore what his predecessor Plato said about women: they can also be rulers of his Republic. But Aristotle also invented logic and was the first empirical scientist who was interested in all things living and dead. He invented the complicated system of taxonomy which is still used in the biological sciences.  One could say he is the father of modern science. He also observed that cities whose leaders become motivated by self-interest rather than the common good degenerate into base forms of political systems — democracies, for example, degenerate into oligarchies (as we are finding out to our chagrin). And Heidegger was a brilliant man who made important contributions to philosophy. The same could be said of Plato who wrote the book to which, according to John Dewey, the history of philosophy is merely a series of footnotes. In order to evaluate the greatness of a mind, no matter whose mind is in question, we need to read and consider carefully what that person said.

It has been said that because Thomas Jefferson had illegitimate children with Sally, one of his slaves, we should reject all he wrote and said. This is part of the P.C. movement that is sweeping the academies of “higher learning” as well as the country itself. Now, whether or not this is true, it is irrelevant. We need to separate the man from what the man said or wrote. He was a genius and his contributions not only to political philosophy but even to things as remote as agriculture and architecture are of seminal importance. Again, we need to be wary of the ad hominem argument. Aristotle, Heidegger, Plato, and Jefferson were extraordinary men and their contributions have made us all better informed and a bit wiser. But we need to work our way through their claims carefully.

Ideas stand or fall on the basis of the evidence and support that is offered in their behalf. Why did Aristotle think some men were naturally slaves, for example? It is not an absurd argument, after all, simply because it will offend some people. He looked around and saw a great many people who simply went along with the crowd, who seemed to lack autonomy, the power to think for themselves and take control of situations much less direct the actions of others. Other men, meanwhile, had those qualities and he concluded that some men were natural slaves while others were natural leaders. We blanch at the word “slave,” and well we should. But the fact that Aristotle points to is undeniable: some people would rather follow than to lead. We even find this in considering the corporate ladder where we discover men and women who are perfectly content to remain on the lower rungs rather than to step higher and take on more responsibility. It’s not a foolish thought or a weak argument. It is simply that we are today hypersensitive to certain words — like “slave” or “Nazi” or “closed society” to carefully consider the argument itself.

Real thought moves past the question of who put what argument forward and regards critically the argument itself. Ptolemy was wrong, but we do not dismiss him as a fool. We simply realize that we now know a great deal more than he knew and we realize the mistakes he made. Science, and knowledge generally, moves progressively forward by fits and starts. Trial and error. But the worst thing we can do is ignore the evidence and the argument altogether simply because we don’t like the person putting it forward. I will allow that in complex arguments where we cannot possibly follow the reasoning process we are warranted in rejecting the claims of those with vested interests in the outcomes. But, in general, critical thought demands that we focus on the ideas themselves regardless of who out them forward.