PBS is hosting a series on the brain, appropriately titled The Brain hosted by Rice University Neuroscientist David Eagleman. I watched the first episode last week and found it highly informative and entertaining. People have wondered what scientific achievements of the 21^st Century could rival those of the 20^th Century—relativity theory, quantum physics, DNA and molecular biology, and big bang cosmology. My guess is that this century will be the Century of the Brain, that is, we will finally gain an understanding of the brain that is both detailed and comprehensive, reductionistic and integrative. The brain revolution will not only be a revolution in science, but a revolution in thought and culture, even challenging our very self-image. We will finally collectively have to come to terms with Daniel Dennett’s statement that, yes, we do indeed have a soul, but that the soul is composed of a hundred billion tiny robots, (neurons). Put another way, the brain revolution will be the completion of the Darwinian revolution, finally and fully incorporating even consciousness into the biological world.

Stupendous progress has already been made, and The Brain seems to be an enjoyable primer. However, philosophers have the role of language nannies, and there is some inexcusable looseness in the way that Eagleman expresses his insights. Of course, this is a popular program, and you do not expect the rigor of a professional journal. However, precisely because it is a presentation intended for public consumption, it is important that the language not convey impressions that mislead and perhaps undermine the whole project. For instance, in the first episode Eagleman repeatedly said that the brain constructs reality. We automatically think that the world is as we see it, says Eagleman, but, in fact, the world is constructed by our brains.

I hope that he did not mean this entirely literally, and that it was exaggeration for rhetorical or pedagogical effect. Taken straightforwardly, saying that the brain constructs the world would seem to imply, for instance, that there are no cats. Rather, all of our perceptions of cats are created ex nihilo and in their entirety by the brain. There are no feline entities “out there” to be recognized and perceived by the brain. Rather, feline reality, like all other reality, is purely and simply a construct of the brain. In other words, when Eagleman says these things he sounds like the neuroscientific equivalent of Bishop Berkeley. There is no external, objective world of subsistent entities that we confront in our cognitive/perceptual activities; such a “world” is an internal creation. Further, Berkeley retained a degree of objectivity by positing God as the being whose activity maintained the tree in the quad even when no one was looking. But if the brain creates reality, we seem to be left with a forlorn solipsism that is as bad as a brain in a vat and does not even have a vat.

I take it for granted, then, that Eagleman, as he seemed to indicate on other occasions, did not mean to say that the world is literally constructed by our brains. What, then, did he mean? Galileo distinguished between primary and secondary qualities and Locke gave the most famous statement of that distinction. Colors, and the entire world of qualia, are, of course, created by the brain in response to information from the external world. Physics knows nothing of “red” except as a roundabout way of referring to light within a certain range of wavelengths. On the other hand, when I perceive a car as being bigger than a breadbox, I seem to be perceiving something as it is in that sense. Is the talk about the world being constructed just a hyperbolic statement of the familiar primary/secondary quality distinction? Whatever he meant, clarity is a virtue even in popular programming.

Eagleman also talked about the differences between individual brains. He said that brains are as different and unique as snowflakes. Many will presumably take comfort in finding that their brains are different from Donald Trump’s. He also talked about how individual brains “construct” reality differently. He spoke about those who experience synesthesia as “constructing” the world differently from others. Of course, there are many profound differences of perception, and, as the late, great Oliver Sacks showed in his many books, disease or damage can cause remarkable and sometimes disturbing changes in how individuals perceive.

Again, though, it is surely an overstatement to say that we each construct reality differently. We interact successfully in many complex ways and carry out many different coordinated tasks, and it would be very hard to understand how we could unless we shared experiences. We all enter the stadium by the gates, but if everyone were constructing his or her own reality we would expect many to construct a brick wall or a sheer precipice or a charging bull instead of a gate, and chaos would be expected. That we communicate semi-successfully with language seems impossible unless there were a shared basis of experience. As Hume observed long ago, our successful practical references to “this house” or “that table” seem to presuppose shared experiences of things like houses and tables. Wittgenstein put it even more strongly when he insisted that there could not be a private language. But if each individual brain constructs its own private experience, then must it not also be inventing and applying a private language?

Recent discussions here at SO have bemoaned the failure of some popular scientific authors to make distinctions or address points that are basic for philosophers. Sounds like the same thing applies to popular programming about neuroscience.