21. Dan Dannett
Philosopher and scientist Dan
Dennett argues that human
consciousness and free will are
the result of physical processes
and are not what we traditionally
think they are. His 2003 book
Freedom Evolves explores the
way our brains have evolved to
give us -- and only us -- the kind
of freedom that matters, while
2006's Breaking the Spell
examines religious belief through
the lens of biology.