In another life, you two were unable to connect in any long-term, meaningful way: Perhaps one of you betrayed the other, inhibiting trust and intimacy between you; or maybe outside circumstances did not permit you to be together for any meaningful length of time. Either way, that old feeling of instability and distrust is still present between you, only this time around, it's quite possible that you will project your own fears of commitment onto your lover. You'll certainly find them unreliable, if exciting; but they'll grow to perceive you as being a bit of a stick in the mud, finding your adherence to logic and fact annoying.
They want to range far and wide in their thinking -- a quality you're actually quite attracted to, because you subconsciously wish you could do more of that yourself. But your conversations will be strange, hectic, uncomfortable; you won't be able to communicate well, and this person's ideas may even set you on edge. And maybe that's a good thing. If you've grown too comfortable in your thinking, you need someone to shake you up a bit -- to remind you that there's a wide and limitless world out there, ready for you to discover its secrets. That's the best that you can get out of this relationship: a reminder to open your eyes and your mind.