Offering both a general explanation of the way the mind works and a compelling humanistic defense of the value of science and rationality, Calne shows that reason has no direct links to the brain's pathways of pleasure and satisfaction that motivate our behavior. Reason is simply a powerful tool put into the service of goals it cannot determine or change. Within Reason delineates how reason - through its deployment in all domains of human endeavor, from science to religion, from ethics, commerce, and government to art and music - has enabled mankind to achieve dominance over all other forms of life without providing any specifiable content, beyond survival, to the meaning of existence. Echoing the great religious and philosophical traditions but written from the perspective of a neurologist, Within Reason offers a new picture of the role of rationality in both evolution and daily consciousness.