Here is my sketch of the emergence* of a star from t1 ---> t4. At each step of the way, the star gets bigger and brighter. Emergence becomes obvious at t4, when a new process (nucleosynthesis) gives rise to new elements not present before (after t3, the star would by itself get smaller and brighter). Why does this happen? The approximate picture we have is based on quantum mechanics and relativity.
*I've been trying to present a sketchy picture of emergence, to get out of the reductionist physicalist model that talking about consciousness is just talking about brains. If you want to understand the problem of freedom vis-a-vis predeterminism, you have to look no further than this problem. I suggested to you that the mind can be seen as irreducible to physical processes. Under this picture, the mind is still caused by the brain, but exhibits properties that are non-reductive, such as intentionality.