Cognitive liberty is the concept that an individual has absolute sovereignty over their state of consciousness, as long as it does not infringe on the rights of another. This includes the use of meditation, prayer, and psychoactive drugs.

This great BBC clip shows how certain animals can be put into hypnotic trance. Evolutionary biologists theorize that these states may be used as a defense mechanism to avoid predators.

Fellow atheists Richard Dawkins, a British evolutionary biologist, and Daniel Dennet, an American philosopher of science, discuss the meaning of life and death.