Is it dumb to assume that the universe has always existed

I hear both theists and atheists claim that there had to be a first cause. I've always thought that the universe has always existed, whether small or big or empty or whatever.

Our finite minds cannot truly comprehend infinity. It's not dumb at all to "think" the universe (or 'multiverse') has always existed, although I wouldn't "assume" as much.

This is a question that religion(s) provide faith-based and dogmatic answers to. Science is far from answering it, but we are getting a better and better understanding of the universe through quantum physics, astronomy, chemistry, astrobioloy, etc., etc.

Ultimately, I don't believe anyone can say so with certainty either way. (At least not today.)

Well it depends on how you view things. If you believe in god, then god always existed and then created the universe x years ago. Although, believing that the universe always existed through the big bang can be tricky. Supposedly the universe "bangs", or expands out, then gravity crushes it back down then it repeats. However the universe is constantly expanding due to dark matter and energy, in theory. So Its not dumb to assume, but material things dont just appear, or are eternal. So for me the universe was created by god, and from what iv gathered its the most reasonable explanation. Hope it helps

The Big Bang is a fairly widely accepted theory. However, time and space are related, so it could be argued that time did not begin until the universe did. In that case, technically the universe has "always" existed as "always" only covers events since the beginning of time.

This idea has been proposed before, and even accepted in the scientific community. Do a search on the Steady State Theory (although it really should be called "Steady State Hypothesis"):