An Argument Against Idealism

An Argument Against Idealism

Imagine we lived in a world in which idealism was the dominant philosophy (in fact, it is the actual world, but that’s another story). The prevailing doctrine is that everything that exists is mental, i.e., a state of consciousness. Not just the mind itself but also the so-called physical world—mountains, molecules, the brain. All these things consist of ideas in the mind, specifically sense experiences of certain kinds—for example, episodes of seeing the thing in question. To be a brain, say, is to be a sense experience as of a brain. Physical objects are really collections of sense-data, as the terminology has it. These sense-data may exist in the human mind or God’s mind or just in my mind (solipsistic idealism]. Physical objects are reducible to such mental entities; this is their essence, their mode of being. Everything has a mental nature.

But suppose there is opposition to such a doctrine: some people firmly believe, eccentrically, that some things are inherently not conscious states; their essence is to be not-conscious, mind-independent. Their battle-cry is, “The not-conscious world is what makes idealism metaphysically impossible”. They reject the claim that physical objects are reducible to sense experiences. The idealists wonder what else these objects could be: it would have to be something unknown, of an unfamiliar nature, a mysterious substance of some sort, subject to skepticism. It would have to be something there is nothing it is like to be, but what would that be? Everything we really know is like something—visual experiences, pains, etc. They have trouble getting their minds around this supposed non-mental reality: how can we even think of it? However, the anti-idealists have an argument that they believe can break this stalemate of intuitions and settle the question once and for all. It is quite an ingenious argument, centering on a conceptual claim. They point out that everything conscious is such that there is something it is like to be it: therefore, it is only possible to grasp a given type of mind by sharing it. You only know what it is like to be a human by having human experiences—it can’t be done from no “point of view”. It takes one to know one; you can’t (fully) know what is like to be a bat because you aren’t one. This property of consciousness they call subjectivity: you can only form a concept of another’s mental state if you are a subject similar to the other subjectively—if you are mental birds of a feather, so to speak. But this is not true of physical states: these you can grasp even if you don’t share them—you don’t need to be a mountain to know what a mountain is; you don’t need to share a bat’s brain to know what a bat’s brain is. In short, no point of view is built into physical concepts: they can be grasped from any point of view. You can do physics if you are human, Martian, or Vulcan—or any species with the requisite intelligence. You can do geometry even if you are not yourself similarly geometrical; you don’t need to be Euclidian in order to understand Euclidian geometry, say. The physical may be defined as whatever there is nothing it is like to be, so there is no like that you must share in order to grasp it. But then, it is not possible to reduce the physical to the mental, because these are concepts of a different order, denoting properties of different kinds. It would not be possible, say, to reduce the physical brain to sensations as of brains, because such sensations would embody a distinctive subjective quality graspable only by beings that have similar sensations; but that is not true of the brain itself, because that can be grasped by beings with arbitrarily different types of sensations. Thus, there must be more to reality than is contained in sensations of reality—the physical cannot be the mental. Physical things are essentially objective: they can be grasped from many points of view and therefore cannot be subjective in nature. Things there is nothing it’s like to be cannot be reduced to things there is something it’s like to be. Therefore, idealism must be false: it tries to explain the objective in terms of the subjective. It cannot be an accurate account of things that lack consciousness, precisely because it explains everything in terms ofconsciousness. The body cannot be explained in terms of the mind, on pain of subjectivizing the body.

Clearly, this argument parallels a familiar argument against reducing the mind to the body; it simply reverses that argument. If the familiar argument is valid, then so is this one. Thus, that argument defeats bothmaterialism and idealism in one fell swoop. It can be used against Hobbes but also against Berkeley. It can be used against physical anti-realism as much as against reductive physicalism. Basically, the argument is that a color-blind man cannot understand color vision but he can understand the brain science of color vision (and the rest of physics). For if he could not, the brain would not be a physical object, which it is. The objective cannot be reduced to the subjective, as the subjective cannot be reduced to the objective. The view from somewhere cannot be reduced to the view from nowhere, and the view from nowhere cannot be reduced to the view from somewhere.[1]

[1] Is this argument perhaps just a little bit too powerful?