‘But there’s a consensus!” shrieked the bossy environmentalist with the messy blonde hair. “That, Madame, is intellectual baby-talk,” I replied.
I was about to give a talk questioning “global warming” hysteria at Union College, Schenectady. College climate extremists, led by my interlocutor, had set up a table at the door of the lecture theatre to deter students from hearing the skeptical side of the case.
The Greek philosopher Aristotle, 2,300 years ago, listed the dozen commonest logical fallacies in human discourse in his book Sophistical Refutations. Not the least of these invalid arguments is what the medieval schoolmen would later call the argumentum ad populum — the consensus or headcount fallacy.
A fallacy is a deceptive argument that appears to be logically valid but is in fact invalid. Its conclusion will be unreliable at best, downright false at worst. One should not make the mistake of thinking that Aristotle’s fallacies are irrelevant archaisms. They are as crucial today as when he first wrote them down. Arguments founded upon any of his fallacies are unsound and unreliable, and that is that.
Startlingly, nearly all of the usual arguments for alarm about the climate are instances of Aristotle’s dozen fallacies of relevance or of presumption, not the least of which is the consensus fallacy.
Just because we are told that many people say they believe a thing to be so, that is no evidence that many people say it, still less that they believe it, still less that it is so. The mere fact of a consensus — even if there were one — tells us nothing whatsoever about whether the proposition to which the consensus supposedly assents is true or false.