What's inner life though? I find my tangled web of intricate ideas, funky theories, and absurd fantasies having a bit more depth than an INFP with a couple imaginary friends, but that's because I'm an INTP.
I'd think of mine as really clear and void until I get some sort of stimulus. From that point on I can maintain and persist and constantly add newer levels of intricacy but it's dependent on that spark of curiosity. Some days I just don't have it and I feel pretty empty. That's where drugs of any sort are to be kept out of my presence. Except caffeine. I'll make an exception for that.
My cold, snide, intellectual life is just a veneer, behind which lies the plywood of loneliness.
And why are there only introverts in that list, aj?
Even though I am an extrovert I know I think, feel and imagine a lot more inside my head than I do on the outside. I can drift off for hours if I let go of sensory information. I can build pretty vivid dreams inside my head... It's a lot of training behind that particular thing, though. It's a brain exercise that I do.
First off it requires complete relaxation, silence, comfortable clothes, warmth etc... Wine is good, too. Then slowly put together, say, a library. Add one detail every now and then, and try to hold all of them inside your head. Even the book covers should have names, and the books in the shelves shall have contents. This is a great way of storing information.
Mightier than the tread of marching armies is the power of an idea whose time has come