Bulverism is a rhetorical fallacy that combines circular reasoning, the genetic fallacy and ad hominem with presumption or condescension. The Bulverist presumes that a speaker's argument is false or invalid and then explains why the speaker made that argument (even if said argument is actually correct) by attacking the speaker or the speaker's motive.
Similar to Antony Flew's "subject/motive shift", Bulverism is a fallacy of irrelevanceâÂÂone dismisses an argument based solely on the arguer's identity or motive (real or perceived), but these are mere proxies for credibility (and therefore susceptible to human error and false assumptions); not determinants of an argument's factual validity or truth.
The term Bulverism was coined by C. S. Lewis (after "its imaginary inventor, Ezekiel Bulver") to poke fun at a serious error in thinking that, he alleged, frequently occurred in a variety of religious, political, and philosophical debates.
Lewis wrote about this in a 1941 essay, which was later expanded and published in 1944 in The Socratic Digest under the title "Bulverism". This was reprinted both in Undeceptions and the more recent anthology God in the Dock in 1970. He explains the origin of this term:
The special threat of this fallacy lies in that it applies equally to the person who errs as to that person's opponent. Taken to its logical consequence, it implies that all arguments are unreliable and hence undermines all rational thought. Lewis says, "Until Bulverism is crushed, reason can play no effective part in human affairs. Each side snatches it early as a weapon against the other; but between the two reason itself is discredited."
The remedy, according to Lewis, is to accept that some reasoning is not tainted by the reasoner. Some arguments are valid and some conclusions true, regardless of the identity and motives of the one who argues them.