No, not the luxuriating in physical pleasures, though that, too, was part of the ancient Greek world. The words “cynic,” “epicurean” and “hedonist,” after all, are rooted in Greek philosophical schools. But rather the more rarefied philosophical concept called materialism, which contends that everything can be reduced to the physical, that there is no real entity called a soul.

“Dualism,” by contrast, is the belief that we humans are both physical and … something more.

Many contemporary scientists, delighted by their advances in understanding how the brain functions, have embraced a modern version of materialism. The conviction that we have souls, they patiently explain to lesser folks, is nothing in the end but a misleading product of the electrical activity within our craniums. Our every thought and action, moreover, is predetermined. Just as other physical processes can be predicted on the basis of the array of circumstances at their origin, if we had sufficient knowledge about any individual’s brain, we could predict his or her every action. Free will, to a materialist, is just a persistent illusion.

“The qualities of mental life that we associate with souls are purely corporeal,” Prof. Paul Bloom of Yale, for example, has averred. “They emerge from biochemical processes in the brain.”

A Harvard professor, Steven Pinker, advises us to set aside “childlike intuitions and traditional dogmas” and recognize that what we conceive of as the soul is nothing more than “the activity of the brain.” Nothing but brain cells are evident, after all, in a brain.

But finding no evidence of the soul in a brain is like finding no trace of Yo-Yo Ma in a stereo speaker and concluding that the cello concerto that just ended, and Mr. Ma for that matter, are only imaginary.