In the beginning, there was dualism. Descartes famously posited two kinds of substance, non-physical mind and material body; Leibniz differentiated mental and physical realms. But dualism faced a challenge: explaining how mind and body interact. The mind executes an intention to raise a finger, and behold, it rises! The body brushes against something sharp, and the mind registers pain.
We now know, of course, that mind and brain are intimately connected. Injuries to the brain can alter perceptual experience, cognitive abilities, and personality. Changes in brain chemistry can do the same. There's no "mental substance" that appears along some phylogenetic branch of our evolutionary history, nor a point in ontogeny during which we receive a non-physical infusion of mind-stuff. We've come a long way from Ambrose Bierce's formulation of the mind in The Devil's Dictionary as "a mysterious form of matter secreted by the brain."
In fact, it appears the mind is just the brain. Or perhaps, to quote Marvin Minsky, "the mind is what the brain does." If we want to understand the mind, we should look to neuroscience and the brain for the real answers.
Or maybe not.
In our enthusiasm to find a scientifically-acceptable alternative to dualism, some of us have gone too far the other way, adopting a stark reductionism. Understanding the mind is not just a matter of understanding the brain. But then, what is it?
It doesn't help that many alternatives to the "mind=brain" equation seem counterintuitive or spooky. For example, some suggest that the mind extends beyond the brain to encompass the whole body or even parts of the environment, or that the mind is not subject to the laws of physics.
Are there other options? Indeed there are. But given that mind and brain are pretty heady matters, it helps to think about a more concrete—and tastier—example. Consider baking.
I'm an antireductionist about baking. It's not that I believe in a "cake substance" that's materially distinct from flour and sugar and leavening. And it's not that I think cakes have some magical metaphysical property (though the best ones sort of do). The tenets of baking antireductionism are far less controversial, and they stem from what we want our "theory of baking" to provide. We want to understand why some cakes turn out better than others, and what we can do to achieve better baked goods in the future. Should we change an ingredient? Mix the batter less vigorously?
Answering these questions can appeal to chemistry and physics. But a theory of baking wouldn't be very useful if it were formulated in terms of molecules and atoms. As bakers, we want to understand the relationship between—for example—mixing and texture, not between kinetic energy and protein hydration. The relationships between the variables we can tweak and the outcomes that we care about happen to be mediated by chemistry and physics, but it would be a mistake to adopt "cake reductionism" and replace the study of baking with the study of physical and chemical interactions among cake components.
Of course, you could decide that you're not interested in baking, and thus reject the theoretical constructs of my "baking theory" in favor of chemistry and physics. But if you are interested in the project of explaining, predicting, and controlling the quality of your baked goods, then you'll need something like a baking theory to work with.
Now consider the mind. Most of us are interested in a theory of the mind because we want to explain, predict, and control behaviors, mental states, and experiences. Given that mental phenomena are physically realized in the brain, just as cake properties are physically realized by their ingredients and their interactions, it's no surprise that understanding the brain is incredibly useful. But if we want to know—for instance—how to influence minds to achieve particular behaviors, it would be a mistake to look for explanations solely at the level of the brain.
These reflections won't be news to many philosophers, but they're worth repeating. Rejecting the mind in an effort to achieve scientific legitimacy—a trend we've seen with both behaviorism and some popular manifestations of neuroscience—is unnecessary and unresponsive to the aims of scientific psychology. Understanding the mind isn't the same as understanding the brain. Fortunately, though, we can achieve such understanding without abandoning scientific rigor. Or, to adopt another baking analogy, we can have our cake and eat it, too.