When I was a young child, I naïvely believed anything I experienced or that anyone told me as true. As I started adolescence, I started to question that, and realised that people who tell me stuff might be mistaken, or intentionally lying to me. I became very interested in optical illusions, and realised my senses could be fooled too. I had to rely on measurable, repeatable truth that scientific experts had written in pop science books.
Then I thought about simulations, being in a story (like in Sophie's World), gods, and every other possibility that the entire world I experience is not real and is created to test me, to observe me, indifferent to me and I'm there by accident - whichever it was, I couldn't believe for sure that anyone besides me really existed, or anything I knew through my senses. Only my logical reasoning could be trusted. I am doubting therefore I exist, but I couldn't know anything else for sure.
Until recently, I realised when I was ruminating one time, and thinking about which is better: truth or happiness. Most of the times I'd ruminated, I knew I'd come to the conclusion that I'd rather be right than happy. I had logic to back this up, it's more important to know the truth because then I'm happy about being right. But when I'd been happier, I thought being happy was more important than being right - after all, what's the point of being right if it doesn't bring you pleasure, seeking pleasure and avoiding suffering being the whole goal of life?
I realised that what I thought was logical reasoning to support my conclusion wasn't logical at all. It was a rationalisation to support whichever conclusion made me happier at the time. When, for chemical reasons in my brain, I was happy, I wanted to remain happy. So I'd subconsciously convinced myself that I had logic to convince myself that happiness is preferable. When my hormone levels were low so I was feeling down, telling myself that at least I feel better because I know the truth is a way of coping.
And I realised that when my 'logical' reasoning is just a rationalisation for an emotional state caused by brain chemicals and my body, I can't trust any 'logical' argument my brain thinks of. I don't exist because I'm thinking, I exist because I have an innate sense of existing. So therefore, I can't trust anything I think is logical. But wait, that there is a logical statement! So I can't trust it either! And so on... aaaAAARGH!
The more I try to find truth, the less I find I know. I somehow get even more agnostic than I thought it was possible to be, I at least thought, 'Alright, I have no idea what the universe is, but as an external observer I know that I exist.'
I am no longer an external observer! My observations about how my hormones and body affects my emotions, which in turn affect how infuriated I am at the fact that I don't know stuff, that I don't have free will - not the other way around - means I can't even think anymore, as my brain is part of the compromised system. I am compromised.
The more I learn, the less I know.
We may be part of a simulation. Our entire universe may be a microscopic component of a much larger one. We may be weird 3 dimensional beings living on a planet inhabited by beings living in other dimensions that we cannot perceive. Their actions may affect our lives.
There are so many possibilities, I don't think it would ever be possible to truly know anything for certain.
I don't know for sure what I am, where I am, or why I am. But I am.
Other people and animals seem to have this same knowledge of their own existence. So I try to treat all humans and animals as I would like to be treated.
We don't know if we have a purpose but being kind, helping others, spreading joy and finding peace in beauty and love seems to be a pretty good way to go for me.