Arguments against the existence of god
There are an infinite possible number of gods. Over a thousand different denominations of Christianity alone, all with their different beliefs on who or what god is. Surely it would be impossible to rule them all out. However if we zero in and examine a theistic claim about a specific god's nature or character, we can draw certain conclusions based on what we've learned about the world through the systematic observations and testing of reality known as science. Despite the theistic assertions that god cannot be caged by science, these specific claims made by the theist can be assessed. As our understanding of the world has increased through science, the gaps that god is able to inhabit have gotten smaller and smaller. With every additional piece of information we learn about the world, the more the constraints tighten on what a god could have or can do. This is perhaps best stated in Stephen Hawking's a brief history of time.
Stephen Hawking in A brief history of time c.1988
- "One can imagine that God created the universe at literally any time in the past. On the other hand, if the universe is expanding, there may be physical reasons why there had to be a beginning. One could still imagine that God created the universe at the instant of the big bang, or even afterward in just such a way as to make it look as though there had been a big bang, but it would be meaningless to suppose that it was created before the big bang. An expanding universe does not preclude a creator, but it does place limits on when he might have carried out his job!"
With our current understanding of our place in the world through biology and astrophysics, we are able to make assessments about certain aspects or claims of god. We have mountains of empirical evidence that life is a result of evolution, not specific intentional creation by an omnipotent being as depicted in genesis. We have mathematical evidence that the Noah's ark could not have stayed afloat during a rainstorm of such capacity that earth's highest peaks were submerged. We have historical evidence that the Israelites were never enslaved by the Egyptians as depicted in Exodus. As it currently stands, our understanding of the universe places the necessity and likelihood of a god or gods, to be on about the same footing as that of the tooth fairy.