Last month,I started a new series of essays on Freud as a philosopher. This month, I want to lay out some of the perplexing philosophical issues that Freud and his intellectual community were confronted with towards the end of the nineteenth century, and how they grappled with them. You simply can’t properly understand Freudian theory, or appreciate Freud’s philosophical originality, without knowing what these issues were and how Freud addressed them.

One of the most central of these was the mind-body problem. The mind-body problem is one of the traditional topics in the branch of philosophy known as philosophy of mind. Unlike many philosophical problems, it’s an easy one to describe. All of us have bodies, and all of us have minds. But what’s the relation between these two things? A bit more precisely, what’s the relation between states of our bodies—in particular, that bodily organ called the brain—and the states of our minds?

For most philosophers, thinking about the mind-body problem is little more than an engaging pastime, but for nineteenth century scientists of the mind there was a lot hanging on solving it. They were trying to figure out just what role brain processes played in explaining our experiences and behavior. They were, on the whole, philosophically sophisticated researchers (much more sophisticated, alas, that most scientists are today). They understood that doing philosophy is an inextricable part of doing science.

Most introductory texts on the philosophy of mind begin with the mind-body problem, because it’s been so important historically. In fact, they usually begin with a chapter on the seventeenth century French philosopher René Descartes. Descartes is important in this connection because he’s closely associated with a take on the mind-body problem known assubstance dualism.物质二元论认为宇宙中有两种事物，物理事物和非物理事物。如果你是一个二元论者，正在清点宇宙中的每一种事物，你可能会把清单分成两栏——一栏标记为“物理的”，另一栏标记为“非物理的”——许多日常物品，如胡萝卜、石头、汽车和人体，都会在第一栏中。但第二列不是空的。它可能包含上帝、天使、鬼魂，更重要的是，人类的思想。

笛卡尔认为人是身体和心灵的混合物，身体和心灵相互作用产生经验和行为。他并没有发明二元论，但他清晰地阐述了二元论，并以在当时看起来很有说服力的方式进行了论证。

Descartes’ brand of dualism had a lot of problems, but to very many people dualism seemed to be the only game in town. The world of subjective experience—of consciousness, feeling, and thought—just seemed so overwhelmingly different from physical states of a physical brain that it seemed crazy to deny that they take place in radically different metaphysical realms.

However, by the middle of the 19th century, dualism was coming under a lot of pressure from developments in the sciences. In particular, the emergence of the new discipline neuroscience seemed to challenge the assumption that the human brain and the human mind were two different (albeit interrelated) things. The challenge was especially acute in the sub-field of aphasiology, which investigated disturbances of language production or comprehension caused by damage to the brain.Ever since Descartes, our capacity for language had been held up as proof that the human mind just can’t be some part of the material world. But the 19th century aphasiologists were discovering that the language capacity is, at the very least, intimately bound up with that squishy globe of nerve tissue between our ears.

尽管科学的进步(不仅是神经学的进步，还有生物学和物理学的进步)对二元论的假设提出了越来越多的质疑，但大多数哲学家和科学家还是死死抱住它不放。The alternative—that human minds justarehuman brains--seemed unthinkable. How could a purely physical thing, a living piece of meat, have hopes and dreams and thoughts and fears?

By the closing decades of the century, aphasiology had become a vibrant interdisciplinary nexus, comparable to cognitive science in the late twentieth century. It was, in the words of the neuroscientist Antonio Damasio, “the intellectual and practical center of neurology but also the focus for scientists and philosophers interested in the field that was to become psychology.”

This is where Sigmund Freud entered the picture. Freud was trained as a neurologist, and included aphasiology among his particular research interests. As a young researcher, he even wrote a book about aphasia (his very first book), which was published in 1891 and was highly regarded well into the twentieth century. Freud had almost certainly encountered the mind-body problem in the philosophy classes and readings from his university days, but the study of aphasia put it front and center for him.

Historians of psychology often say that early on, before inventing psychoanalysis, Freud adhered the mainstream view known asmaterialism，但后来拒绝了这一观点，转而支持心智与大脑不同的观点。这是不正确的。仔细阅读19世纪晚期神经心理学著作的哲学上的细微差别表明，弗洛伊德的知识分子群体中大多数人都是二元论者，而不是顽固的唯物主义者。世界杯赛程2022赛程表欧洲区仔细阅读弗洛伊德的早期神经科学著作就会发现，弗洛伊德属于这一正统立场。世界杯赛程2022赛程表欧洲区

The writings of the important British neuroscientist John Hughlings Jackson—who was a major influence on Freud—are instructive. Like most scientists of his generation, Jackson was philosophically educated (sadly, that’s no longer the case for most scientists), and was alert to the philosophical implications of scientific discoveries. He recognized that Descartes version of dualism was inconsistent with the Law of the Conservation of Energy in physics—the principle that the quantity of energy in the universe remains constant—and therefore that Descartes’ theory had to be rejected. But like many other scientists of the day, he simply traded it in for a different version of substance dualism. Jackson opted for the theory known as “psychophysical parallelism”—the thesis, derived from the seventeenth century philosopher Gottfried Leibniz. It’s the weird idea that physical brains and non-physical minds don’t interact but merely run in parallel, precisely coordinated like two synchronized clocks. Jackson and others resorted to notions like this because the materialist alternative was just too challenging to seriously entertain.

There was another part of Descartes’ legacy that was giving the neuroscientists and psychologists trouble during this period: the idea that the human mind is transparent to itself. This is basically the notion that the human mind isall conscious, and therefore that we can investigate human psychology by introspection. If true, this would place psychology in a category that’s different from all the other sciences. Generally, in science, one tries to draw conclusions that are objectively true. This is only possible if there is intersubjective agreement—which is a fancy way of saying that the thing that’s being observed can be accessed by more than one person. For example, if I’m performing a chemical experiment, other people can repeat and observe what’s being done and what the result of the experiment is. They can validate my observations or hold my feet to the fire by challenging what I claim to have observed. But all of that seems impossible for a subjective method like introspection. And this raises questions about whether it’s even possible to have a science of psychology.

在19世纪，越来越多的证据表明，认为人脑对自己是透明的这种观点是错误的。实验心理学的方法依赖于将实验对象暴露在刺激下，然后让他们报告他们的经历，结果极不一致，而对精神疾病和脑损伤影响的观察非常清楚地表明，我们无法了解自己内心的很多想法。最后，对催眠暗示的研究表明，我们的行为会受到我们完全没有意识到的观念的强烈影响。

Still, the idea that all cognition is conscious was hard for scientists to let go of. To do so required a paradigm-shift of major proportions. In his early years as a neuroscientist, Freud fell in with the conventional view. He believed that mind and brain were two distinct things and that all mental processes are conscious. This all changed in 1895, when he jettisoned the whole Cartesian package and moved to the view that all mental processes are processes in the brain, that all cognitive processes take place outside of consciousness, and that introspection does not give us access to what’s going on in our own minds. This was an extraordinarily radical move, and it coincided with the birth of psychoanalysis.Next month, we’ll dig into some of the details.