Inspired by Dr Adequate's post on unsolved questions on biology ...
1. How does thought originate?
2. How do you recall something from your memory?
Probably these two questions are similar. But I think they are different. May be their mechanism of origin may be similar.
If you believe in mind body dualism, then, they may have an easy answer. But is the mind different from brain? Or is it a 'metaphor' used to signify the collective out put of the brain?