In his book, Intellect: Mind Over Matter, Mortimer Adler emphasized four points. First, intellectual powers and operations of the human mind are immaterial, and the intellect functions with an entirely independent reality. Second, human beings can think about what is totally unperceived by the senses. Third, mind and matter, mental and physical, constitute two distinct realms, the one irreducible to the other. Fourth, an intellectual, rational mind is associated with having a soul that can be immortal, capable of existing apart from the perishable body.