You seem to have forgotten that we are discussing the word athe
ism. This is atheos + -ism.
So what does -ism mean?
Seeing as wiktionary is your preferred oracle :
An ideology, system of thought, or practice that can be described by a word ending in -ism.
If you want the Oxford English Dictionary definition:
atheism, n.
Pronunciation: /ˈeɪθiːɪz(ə)m/
Forms: Also 15 athisme.
Frequency (in current use):
Etymology: < French athéisme (16th cent. in Littré), <
Greek ἄθεος : see atheal adj. and -ism suffix. Compare Italian atheismo and the earlier atheonism n.(Show Less)
Disbelief in, or denial of, the existence of a God.
Note: Atheos + ism, not a-theism (unless you and some random atheist websites are in fact greater authorities on the English language than the OED)
No matter how many straws you clutch at, the 'argument from letters' is both a terrible argument
and it better supports the opposing position.
Why not just argue that the modern definition is better for whatever reason you prefer it? There's no need to pretend it is actually the classical usage as this is palpably nonsense.