Is life Real?

Today in class we had a very interesting discussion about how people's beliefs and religions are what cause war and confusions in the world. It's crazy to think that all of these arguments and discussions are based on the fact that nobody knows what happens after you die. And nobody's ever going to know, so you just don't know if what you believed in your whole life is true, you'll only know when you're dead. This makes me question reality, like how do we know events in history actually took place, if the only proof is written, and people can write lies. This all started when a slide about greek gods came up, how do we know those were fake, I mean they could've been real, and nobody's ever going to know!