Question

According to my inner intuition, the only thing I can know with certainty is that I myself have consciousness. Why is it rational to assume that others do too?
Also, according to the idea that God created the universe in order to attain perfection, one soul going through a journey of self-perfection is enough; there is no real need for all human beings to have consciousness and experiences. It could be that all of existence is just a “set” for the one consciousness that is undergoing perfection. 
Along the same lines—maybe every soul has an entire universe of its own, and in that universe it is the only one that exists. That might also partially solve the problem of evil.