What assumption, you said you're an atheist,as for my belief in god well I highly doubt that the earth could exist with the perfect ratio of molecules for the existence of water and air,not to mention the position of the moon and sun is so perfect that if it were off just by a minute fraction we would either burn up or freeze and what are you gonna say that was all just by chance and earth just happens to be one of the only planets to have all these components come together perfectly,I doubt it.
Than there's the big bang theory that astrophysicists say anywhere from 10 to 15 billion years ago the universe exploded into being and the problem with this is when they are asked what is was before the explosion they say non being and that is analytically false to say that something just exploded into being, for it was in a state of “being” before it exploded, then it just didn’t explode into being from non-being,the point is that space(0)+time(0)+chance(0)=everything,as you can see it is an equation with no numbers in it,it is missing causation.
The law of causality is so fundamental that if I said that the chair you are sitting on, which must have had a beginning, just popped into existence without any cause, you might justifiably think I need a psychiatric assessment and you‘d be right! If at one time there was absolutely nothing that existed, then nothing would exist today. Something had to have existed before the finite, singularity of the Big Bang even.
Something cannot come from nothing.