how brains know reality
Reality and Its Discontents
The comedian Lily Tomlin said that reality is a crutch for people who can't handle drugs. Some philosophers also have a low opinion of reality, seeing it as a mere construction of people's minds or social contexts. In contrast, this chapter argues that the things investigated by science exist independently of our minds, construed as brains. Using perception and inference, brains can develop objective knowledge of reality, including knowledge relevant to assessing the meaning of life. The previous chapter's conclusion that minds are brains has major implications for two central philosophical questions: what is reality, and how do we know it? These questions are interrelated, as consideration of what things exist needs to fit with discussion of what it takes to gain knowledge about those things. For example, an empiricist who believes that knowledge can come only through the senses might conclude that physical objects such as lions and mountains are not real, because we sense only features of them, not the things themselves. At the other extreme, an idealist who believes that reality is inherently mental might also conclude that lions and mountains cannot be said to be real apart from how we think about them. I think that lions and mountains are real, and so are clouds and electrons. But the hypothesis that minds are brains does not support a kind of naive realism according to which things are just as we perceive or conceive them to be. We know enough about how brains work to show that both perceiving and theorizing are highly constructive processes involving complex inferences. Nevertheless, there are good reasons to believe that, when the brain is working well, it achieves knowledge about the reality of both everyday objects like mountains and theoretical scientific entities like electrons. This chapter shows how brain science and philosophical reflection together support a kind of constructive realism, the view that reality exists independently of minds, but that our knowledge of it is constructed by brain processes. I aim to show that constructive realism is superior to alternative theories of knowledge and reality offered by different variants of skepticism, empiricism, and idealism. Skepticism is the view that we have no knowledge at all, so that any talk of the nature of reality is pointless. Some ancient Greek philosophers advocated an extreme form of skepticism according to which neither sensation nor opinion could give us any grounds for separating truth from falsehood. An influential current form of skepticism is found in postmodernist philosophers and literary theorists who view the world as a text open to many kinds of interpretations, none of them demonstrably better than the others. In fields such as history, anthropology, and cultural studies, it has become fashionable to claim that reality is just a social construction, so that the idea of objective knowledge is only a myth. I will try to show how objectivity is possible through the complex perceptual and theoretical abilities of our brains. Brains are not mirrors of nature, but they are powerful instruments for representing it. Empiricism tries to avoid skeptical problems by restricting knowledge to what can be perceived by the senses. From early modern philosophers such as John Locke and David Hume to later thinkers such as Rudolf Carnap and Bas van Fraassen, the restriction of knowledge to sense experience has had strong appeal. I will show, however, that strict empiricism is incompatible both with the neuropsychology of perception and with the practice of science. Our brain processes are, fortunately,
capable of reliably taking us well beyond what is presented to us by our senses. Another approach to understanding knowledge of reality is idealism, which views reality as dependent on or even constituted by minds. This view is more compatible than is empiricism with the constructive nature of perception and inference, but grossly overestimates the contributions that minds make to the world. It leaps from the insight that there is no knowledge of things without construction of mental representations of them to the conclusion that entities are mental constructions. The philosopher Immanuel Kant thought that he had accomplished a kind of Copernican revolution by placing mind at the center of knowledge and reality. But idealism is actually attempting a kind of Ptolemaic counterrevolution, as implausible as reactionary attempts to return the earth to the center of the solar system or to deny human evolution. To develop my alternative, brain-based approach to constructive realism, I will first discuss perception of objects and then move on to how inference enables us to go beyond perception.