Remember what turned Mortimer J. Adler from agnosticism to belief in God: he discovered the difference between humans and all animals, a chasm that no evolutionary leap can span. What makes a human being? Not his skeletal structure or the capacity of his brain. It is the ability, said Adler, to form conceptual ideas and express them in words. Neither conceptual ideas nor the words that express them occupy physical space or have physical substance—but they are real nonetheless. Right here, in this simple truth, the atheist materialist is dealt a death blow.