“Nothing in biology makes any sense except in the light of evolution” (Dobzhansky, 1973). Natural selection is the mechanism that drives evolution (Darwin, 1859), and is the basis of evolutionary biology and evolutionary psychology. Because of natural selection, all human behavior is security-seeking. To grasp why this is so, and why it is so important, requires changing two current understandings of how natural selection works. These corrections unlock fresh insights that revamp present ideas concerning matters as profound and as diverse as human behavior, emotional feelings, belief, attachment theory, moral philosophy, altruism, authority, placebos, culture, and belief in gods. Presented here is a unified theory of behavior, emotions, morality, values, and theology based upon the unifying principle of a security paradigm for the understanding of natural selection: an evolutionary theory of everything.