Argumentum ad Populum

Atheist call-in show hosts like to glibly dismiss some theistic callers as guilty of using the argumentum ad populum; that's the claim that a proposition must be true because lots of people believe it to be true. This is considered an informal fallacy and a fallacy of relevance rather than a formal, or logical, fallacy. But is it really a fallacy? It depends, as we'll see. I'll say right at the top that no less a thinker than Aristotle held that our knowledge is and should be chock full of endoxa, which is Greek for reputable beliefs that almost all people hold without having personally confirmed them. Oops, by dropping Aristotle's name, did I just commit the fallacy of the argument from authority (argumentum ab auctoritate)? We'll see.

When I said above that "it depends," part of what I meant is that it depends on how we phrase the alleged fallacy. "That most everyone believes X is true proves that X is true" is clearly fallacious. But how about this? "That most everyone, including most reputable experts in the relevant field, has believed for a significant length of time and after much debate that X is true indicates that X can be regarded as true by lay people as long as it doesn't clash with other justified beliefs and is in principle open to revision or rejection through counter-evidence (that is, is defeasible)." That doesn't seem so unreasonable, does it?

According to Auburn University philosopher Roderick T. Long, that was more or less Aristotle's view of how people can build up explanations about all sorts of things, from science to ethics. What Aristotle was getting at is this: we all have to start somewhere as we try to understand the world. No one starts or could start from scratch. We are born into a world of parents, teachers, and others from whom we absorb various webs of beliefs, which can contain both true and false propositions. (We don't learn isolated propositions but series of connected propositions.) As we come of age we do not--and could not--sweep all of that away and start over with a blank slate. Rather, we proceed from whatever point we find ourselves. Over time, as the need arises or as our curiosity is aroused, we sift through some of our beliefs to see how they cohere with others we hold, how plausible they seem, how they fare against new empirical evidence, and so on. As a result, some of our beliefs are tossed in the bin as mistaken, some are revised, and others survive intact with more or less confidence. The result is an updated web of belief. This is a lifelong process. The rational approach is to hold all beliefs as defeasible, that is, open in principle to change or disposal in light of new evidence. The only thing that is indefeasible is reason itself because defeasibility requires and presupposes reason.*   

To illustrate the method, Long "borrow[s] an analogy from Susan Haack [Evidence and Inquiry: Towards Reconstruction in Epistemology:] intellectual inquiry is like a crossword puzzle: one starts with answers that initially seem plausible, but every answer is subject to revision in the light of other answers; by the time the puzzle is completed, it is quite possible that none (or some, or all) of the original answers will have escaped revision."

Atheists who feel superior to theists should ask themselves how many of their justified beliefs--about any area of life--have they confirmed personally? No matter who you are or what your field of study or work is, I'm certain the answer will be "very few." It couldn't be otherwise because no one would have had the time, technical knowledge, or expertise to directly confirm everything he knows, using that word in it reasonable everyday sense.

Here's one way Aristotle put it in the Nicomachean Ethics (1145b): "Our proper course with this subject as with others will be to present the various views about it, and then, after first reviewing the difficulties they involve, finally to establish if possible all or, if not all, the greater part and the most important of the opinions generally held with respect to these states of mind; since if the discrepancies can be solved, and a residuum of current opinion left standing, the true view will have been sufficiently established."

In building up our knowledge, it is not where we start that matters but where we go from there. And in many matters, most nonphilosophers won't have to go very far. As Aristotle wrote, "For the 'that' is the starting-point; and if this is sufficiently apparent, there will be no need in addition for the 'because.'"(Roderick T. Long's translation.) If we adopt a reasonable approach--which has been called "negative coherentism" and "reflective equilibration"--we'll be on the best path to objective knowledge about the world. We really have no better alternative if we wish to avoid the untenable poles of radical skepticism and omniscience.

*By reason I include what Ayn Rand called "axiomatic concepts," which cannot be denied without contradiction: namely, existence, identity, and consciousness.