Chemists can tell us how molecules interact and change according to general principles rooted in physics. No surprise there—the relation be- tween chemistry and physics is a textbook example of intertheoretic re- duction in the philosophy of science. Beginning in the mid-twentieth century, biologists began to explain the functions of cells in terms of the molecules that make them up. This has been worked out in detail for many cellular functions and in gist for the rest. Even those special cells called neurons, with their special tricks of signaling and changing con- nections to one another, are being explained in terms of more fundamen- tal physical and chemical processes.
While cellular neuroscientists are steadily filling in our understanding of what neurons do and the molecular machinery by which they do it, systems neuroscientists armed with computational models are showing us how groups of these cells in combinations can do even more tricks. The behavior of large ensembles of neurons can, in turn, be studied by neuroscientists and psychologists by putting people in scanners, stimulat- ing specific brain areas, or observing the effects of brain lesions. Percep- tion, memory, decision making, and many other mental functions have been associated with the activity of specific sets of localized populations of neurons. At this relatively molar level of description, the brain’s oper- ations can be linked upwards to psychology as well as downwards to biology.
It is here, at this juncture between psychology and the natural sciences, that neuroethics comes in. In principle, and increasingly in practice, we can understand the human mind as part of the material world. This has profound implications for how we regard and treat ourselves and each other. It gives us powerful new ways to predict and control human be- havior and a jarringly material view of ourselves. Neuroethics is the field that grapples with these developments.