intp/intj

I'm just another person confused about their type, and I would be very happy if you'd help me out. I've tested in the past as an INTP, but I think that this may be because my surroundings are messy and I don't particularly care about a disorganized room. My computer, on the other hand, is...

Since I've known of MBTI stuff, I've usually tested as INT with a low j. As you can see on this test, they're almost equal. So it's made me wonder... What are the differences between the two INT's?