Hi
Why some great scientists like Hawking and Einstein became atheist?
My guess is that scientist are trained to, cherish and internalize the scientific method, which only accepts EMPIRICAL evidence or evidence/arguments derived from known true statements or empirical evidence as decent evidence/arguments, though often still lacking, and regards everything else as very unrealiable.
Which is the correct approach in science.
But as there is no empirical evidence for God or actually anything supernatural (*), they can see only “lesser” evidence/arguments in favor of God; considering that on the other hand God (or other gods or other supernatural stuff) is supposed to actively interact with the natural world, gives rise to suspicion, that most or all of the “lesser” evidence is artificat, error or faked.
Coupled with the fact, that those religious/supernatural claims, which included material which should be open to empirical investigation, always turned up to be false (e.g. the Zeus causes lightning, that sacrifices improve harvest output, that praying consitantly improves health outcomes during illness, …), they so to say “smell a rat” and consider it to be the most likely explanation, that all religious/supernatural claims are actually based on faulty evidence and therefore can be disregarded.
(* More precisely, for all supernatural claims so far attempted to be studied empirically, it was always true that the more precisely the issue was studied the more any potential empirical evidence turned out to be an error, artifact or just completely faked.)
The philosophical error some of them make in my opinion is that based on this approach on has to conclude that we are nothing but chemical and biological reactions; our feelings, pain, joy, hope, despair, dreams and horrors are nothing but chemical and biological reactions with in no relevant way different from whats going on in some microorganisms. Hence, one would have to conclude that the entire ethical basis of our western societies, e.g. that humans have rights, is just an arbitrary choice among a myriad of potential values with no evidence in favor of one choice over another; hence, there is no wrong with a group like IS that simply makes a different choice in this moral spectrum, as their different choice just leads to different biological and chemical reactions happening in their sphere of influence.
Or as Monthy Python put it quite shortly:
“You come from nothing, you go to nothing, what do you lose? Nothing.”
Which means there is absolutely no reason to let someone live or kill someone, in 200 years we are anyway all dead.
So effictively their deny their own right to life and taking them at their word, it would be ok to kill them or anyone else or kill no one, it just changes which reactions are happening on this piece of rock called earth.
They try to avoid this, by claiming that conscious creatures (e.g. humans, apes, maybe some other) deserve special privilege and claim without any EMPIRICAL evidence that the life of such creatures is somehow worthwhile, this based solely on the argument that the attitude spelled out above is cruel or inhuman or so, so just based on their personal disgust.
So their error is, that by only accepting empirical evidence in respect to issues pertaining the meaning of life, they end up with a philosophy that is based solely on feelings and whims.