The study of existence, knowledge, values, reason, mind, and language. Or well, everything.
Being able to entertain new thoughts and hypothesis and try and ground them in the basis of our perception of the world is interesting.
In any way, it is an interesting subject I don't know much about.
Stoicism helped me build the ability to care about the things in my power to change, and not stress about things that aren't.
Being able to entertain an idea without fully accepting or rejecting it is a good start
Not dismissing new ideas simply because they seem contrary to what one already knows, but exploring them on a subjective basis and coming to a informed personal understanding.
If you've already decided what's possible and what isn't then you've set up walls you'll never overcome.
Someone who is interested in actively exploring the nature of mind from the inside without resorting to wild, unhinged speculation unconnected to intersubjective reality.