There are those who argue that people can never understand consciousness. The mystery is too deep. Colin McGinn, a philosopher from Rutgers University, argues that because our brains are products of evolution, they have cognitive limitations. Just as rats and monkeys cannot even conceive of quantum mechanics, humans may be prohibited from understanding certain aspects of existence, such as the relation between mind and matter. He says that for humans to grasp how subjective experience arises from matter might be like "slugs trying to do Freudian psychoanalysis--they just don't have the conceptual equipment." Consciousness, in other words, may remain forever beyond human understanding.