My boyfriend thinks through everything?

Okay so I've been with him for 2 years now. Hes incredibly intelligent and sweet. Hes a huge nerd with a weird fun personality. But he does this thing that I just cant understand. He enjoys thinking. A lot. I overthink, but I overthink in the sense of what ifs and anxiety and such. He overthinks as well, but not in that sense. For example, he will evaluate a trait about himself that he knows 100% is true, or close to, but then go through WHY that trait is true and why he feels that way. It doesn't really seem unhealthy I dont think, I mean the way I overthink is way more harmful that's for sure xD but it's just very odd...things everyone just knows about themselves and doesn't question WHY, he will question why. Not because of anxiety or even because hes unsure most of the time, but just because...he does. We've been together 2 years so I love him and understand him on a lot of levels, just not this one. Can anyone maybe help me out with maybe why hes like this...?