Cats and dogs appear to be conscious. Chimpanzees appear to be conscious. All people appear to be conscious. People can lose and regain consciousness without any sign of divine intervention. A Greek philosopher once said that a blow on the head produces different effects to a blow on the foot and this cannot be due to an immaterial soul.
People can alter their consciousness with drugs , for example, alcohol.
There have been experiments where stimulating particular areas of the brain have brought very specific memories into a person's consciousness. Consciousness appears to be as natural a phenomenon as sneezing. It is the basic assumption of science that we can find scientific explanations of natural phenomena. Apparently, this scientific assumption ultimately derives from the Christian view that God has created a universe which is orderly and rational and can be understood by human beings. Of course, we do not yet have any good scientific explanations of consciousness.