Sageous, my own belief system conforms exactlly with what you are saying. Many may be offended, but here it goes. 1) the nature of the world is a dream/ thought energy taken form. All the basic e=MC2 stuff. The rules are clearly defined regarding local gravity and such, but it is dream based. Old concept, a bit like the matrix. 2) One thing that can exist is an animal life form composed of nothing but chemical reactions. The reactions can appear like personality, likes, fears, and so on. Humans in this case can be such an animal. The animal is simply a construct of physics, but capable of intelligent behavor and personallity. 3) A seperate thing also can exist. It is the same as your 'sentience'. It appears to develop some how in animals. It can also be born into them. The idea is some humans are reincarnated entities, who choose (are forced/karma) to incarnate in the physical world. They can carry some element past death and start with a new body. Perhaps some may even take up residence in a body that is older, explaining the sudden development of 'sentience' or 'an entity.'

It leaves 3 options. the person you are dealing with may 1) be nothing more than a human animal 2) be an animal that is coexisting with an entity 3) a human animal somehow creates a new entity

I say some pretty weird stuff, but all the ideas are standard in some religions.