[4] There has also been an increase in evidence that behavior results from cognition which in turn requires consciousness and the brain.
It is a problem of the philosophical idea known as solipsism: the notion that for any person only one's own mind is known to exist.
[5] Phenomenology studies the subjective experience of human life resulting from consciousness.
List argues that there exists a "quadrilemma" for metaphysical consciousness theories where at least one of the following must be false: 'first-person realism', 'non-solipsism', 'non-fragmentation', and 'one world'.
[8] Caspar Hare has argued for similar ideas with the concept of egocentric presentism, in which other persons can be conscious, but their experiences are simply not present in the way one's own current experience is.