On the other hand, if one is a theist then one is usually disposed to think that there's more to reality than just physical matter. Reality, on this view, includes non-physical, immaterial mind and/or soul. This view is usually referred to as substance dualism.
Thirty five years ago a philosopher named Frank Jackson posed a clever thought experiment which he believed refuted physicalism. There's an interesting discussion of the strengths and weaknesses of Jackson's thought experiment, called Mary and the Knowledge Problem, by Ari N. Schulman at The New Atlantis. Schulman begins by explaining Jackson's argument. He writes:
[T]he thought experiment was proposed by Australian philosopher Frank Jackson in a 1982 paper. It was posed as a challenge to physicalism, the school of thought that holds that the mind is purely material, made solely of the stuff of rocks and meat, fully explicable by physics and chemistry. Physicalists regard the common-sense view that the mind is special — whether because it’s self-aware, can think and feel, or has free will — as an illusion.It's not surprising that the "knowledge argument" hasn't persuaded many, if any, philosophers to abandon physicalism. To give up physicalism (or dualism) is not like giving up one's belief that one's favorite baseball team will win the pennant this year.
Aiming to refute physicalism, Jackson asks us to imagine a scientist named Mary, who is so brilliant that she acquires all of the “physical information there is to obtain” about the workings of vision. Mary, that is, learns everything there is to know about how various wavelengths of light stimulate the retina, the neurology of the visual processing system, how this system interacts with the speech centers to produce spoken descriptions of images, and so on. The catch is that Mary has lived her whole life in a room in which everything is entirely in black, white, and shades of gray, including her books and the TV monitor she uses to investigate the world.
One day Mary is released from her room. For the first time, she sees colors with her own eyes. The question is: Does Mary learn something new?
The intuitive answer for most people is: yes, of course — Mary learns what it is like to see color. She learns about the redness of a rose, the blueness of the sky. But recall that Mary already knew everything physical about vision. So whatever it is that Mary learns is not encapsulated in physical descriptions. We can conclude, then, that there are such things as nonphysical facts about vision, meaning there must also be nonphysical properties of vision. In short, there is something special about the mind, and physicalism must be false.
The conclusion may strike many readers as obvious, but physicalism is the orthodoxy among today’s physicists, biologists, and philosophers of mind. To the physicalists, their position is the beginning and the end of the modern scientific project: in principle, a core metaphysical commitment that distinguishes modern science from its forebears; in its particulars, the final theory that is supposed to await us on the distant day when science is finished.
Peruse the pop-science headlines on any given day and read about how “we now know” that the love you feel looking at your child is actually just oxytocin in the limbic centers of the brain, a development that just happened to help our ancestors outbreed their neighbors, who apparently felt for their children the way we do about a plate of wet bread. The sense that your soul just died is a sign that you are now bending properly along the great de-spiriting arc of history. Thus, the knowledge argument seems to provide a welcome bulwark against the rising tide of physicalism, a relief to those who believe that love is love, whatever else it might also be.
Of course, as clear and intuitive as it first appears, Mary’s Room, like every other question of mind, is not nearly so simple. It would be surprising if a centuries-old philosophical project could be crumbled at its foundations by the kind of lesson taught to four-year-olds in preschool. Fittingly, then, despite three and a half decades of sustained discussion, the knowledge argument has apparently not won a single academic convert to dualism, the opposing set of theories holding that the mind is not entirely physical, or that mental and physical properties are distinct.
Though it is now perhaps the go-to example of an argument against physicalism, philosophers have offered compelling reasons to doubt it. The knowledge argument seems largely to have entrenched the opposing sides, providing each with an ever more elaborate set of rationalizations for its existing views.
Physicalism and dualism are conventionally seen as enemies, and with good reason. Each position is as much a sustained rejection of its opposite as it is a positive program of explanation in its own right. But as we will see, the mutual hostility of modern physicalism and dualism conceals a deeper convergence.
Understanding the thought experiment requires a return to foundational concerns about how we move past subjective experience to achieve objective knowledge of the world. These questions in turn point back to the genuine mystery of mind — of how it is that certain bits of dust, arranged just so, become capable of pondering the infinite.
To yield on a matter as fundamental as the ultimate nature of the universe would rock one's entire worldview, and would have grave implications for one's belief in God. People only undergo a revolution in their worldview as a last resort and then only with much psychological and emotional agonizing. As long as there are any arguments at all that can be clung to to keep one from being blown away in the gale of opposing evidence those arguments will be tenaciously latched onto.
This is not to say that the counter-arguments invoked against Mary aren't good, only that it usually takes more than arguments to persuade someone to abandon a supporting pillar of his or her worldview.
Schulman goes on at length to examine the arguments on both sides of the issue in what is a very thorough and informative essay. Philosophically-minded readers may want to check it out.
