By soul I mean the ineffable essence of a self.
It is inextricably embedded in materiality, but is more than mere material.
A soul is first of all a genome, a unique fusion of the genomes of a father and mother, and therefore of a line of ancestors that reaches all the way back to the origin of life on Earth. I share genes with the hummingbird and gecko.
A soul is a body, exquisitely constructed in the womb as the genome expresses itself in bone and tissue.
A soul is an immune system, a way the body distinguishes self from non-self, thereby maintaining the integrity of the soul against forces of disintegration.
A soul is the body's awareness, a thing that grows from the faint spark of the fertilized egg to the reflective perceptions of maturity. Awareness can be cultivated, nourished. Awareness confers -- ah, here, here is the nub -- self-awareness.
A soul is an ever-growing storehouse of memories, utterly unique to each individual. These memories can reach across space and time far beyond a self's immediate environment. Education is soul-making. The Cat in the Hat is soul-making. War and Peace is soul-making. A scanning electron microscope image of an ant's eye and the Hubble Ultra-Deep-Field Photograph are soul-making.
And nature. There is no soul-making activity so rich in spontaneous possibility as immersion in the natural world. There is more to wonder at in a square-foot patch of weedy ground than in all the libraries on Earth.
