Many people are mistaken about the etymology of the word “atheism.” They think it comes from an alpha-privative negation a- joined with theism, that is, they think
atheism = a- theism
atheism = the negation of theism
That is not where atheism comes from, however. ‘Atheism’ is in fact an older word than ‘theism.’ It comes originally from the Greek ἄθεος meaning ‘godless’ or ‘without god’. The -ισμός is a later addition, which means “doctrine of” or “teaching of.” Hence
atheism = ἄθεος -ισμός = atheos -ism
atheism = the doctrine or teaching of Godlessness, i.e. the teaching that there is no God.
Here’s a breakdown of the history:
As noted above the new redefinition of atheism as “lack of belief in God” was a bit of philosophical slight of hand (or more precisely slight of language, or even more precisely sophistry, perpetrated Antony Flew and a few of his atheistic fellow travelers starting in the early 1970s. Flew was probably the most consistent atheist apologist in philosophy through most of the 20th century—and it is worthwhile to note that late in his life, when retired and finally with enough leisure to read Aristotle carefully for the first time, Flew was rationally forced to reverse his lifelong position and embrace rational theism. Maybe he should have read Aristotle earlier in his career? Kudos to Flew for having the intellectual and philosophical integrity to publicly reverse himself on the very position he had built his entire philosophical career maintaining. That extraordinary act of philosophical courage and integrity almost makes me forgive him for perpetrating this pernicious bit of sophistry: