B
Blue_Horizon
Guest
It is a little more complicated than this I believe.Sincerity of course does not excuse anyone’s sins.
We know how sincere the devil is about destroying us all.
Natural angelic minds, even including the devil, are unable to sincerely deny the existence of God because the perspicacity of their intellect is such that it is as impossible for them to sincerely deny God 's existence as it would be to deny their own existence. It is a self evident reality for them.
This is basic Aquinas.
For the natural human mind it is entirely possible to be non culpably unaware of God’s existence because this is not a self-evident truth in the same way. All the more so due to the intellectual wound caused by the Fall.
I believe what is meant when we colloquially speak of sincere atheists is that they are non-culpably unable to apprehend the existence of God by reason.
Further, it also suggests that God has not yet extended to them the same strength of graced opportunities for coming to know him through faith either.
For these reasons I would be slow to say that lack of certitude re the existence of God is “grave matter”. Nor can we reasonably assume culpability if atheists are sincere (ie naturally virtuous in every other way).
If this be the case such “sincere” atheists may perhaps not rightly be called either material or formal sinners.