Illusions of Mind

Illusions of Mind

Is it possible to maintain that we know other minds better than we know other bodies—or even our own body?  Can we be more skeptical about our knowledge of bodies than our knowledge of other minds? That sounds unlikely, given that we infer other minds from other bodies: we see other bodies and then conjecture what lies behind them mentally. We know external bodies better than we know external minds, don’t we? Isn’t that an axiom of epistemology? But there is a difference between the two sorts of knowledge that undermines this confidence: knowledge of other minds is not subject to visual illusion. There are no optical illusions of other people’s mental states, as there are no optical illusions of one’s own mental states. Our eyes never deceive us in this way. There are many optical illusions regarding physical objects, often quite striking: the visual brain is prone to these sorts of errors; there are glitches in the system. I needn’t give examples; they are a commonplace of psychology textbooks (the Muller-Lyer illusion will suffice to fix ideas). In addition, we have visual hallucinations in which whole scenes appear to us that don’t exist. You can’t believe your own eyes; they lie to your face. The visual system is inherently given to these illusions. The skeptic, then, can exploit them to undermine our knowledge of the external world—we might be under a giant sensory delusion. Perhaps my experience is not veridical but illusory; we can’t be certain this is not so, given the prevalence of illusion. It can even be argued that our impressions of color are visual illusions, since color does not really belong to objects. The visual system is set up for error, intrinsically fallible, a potent source of false belief. Knowledge based on it is shaky at best and non-existent at worst. It is an unreliable informant.

But the psychology textbooks record no examples of visual illusions of other minds. We don’t have visual impressions of other minds that mimic standard visual illusions: we don’t look at a bodily stimulus and seem to see a mental state that isn’t there. We may think a mental state is there that isn’t, but we don’t see such a state—we don’t have a visual experience as of a non-existent mental state. Our eyes don’t deceive us in this way. There is no Muller-Lyer illusion of the mind, or duck-rabbit drawing, or any other of the many illusions our eyes are prone to. Our perception doesn’t work this way. In fact, our perception of other minds is in this respect like our perception of our own mind: neither do we have illusions of non-existent mental states in ourselves. You never perceive a belief as a desire, say, or a belief that p as a belief that q, or an emotion as a thought. You are not capable of this kind of error: introspection is not prone to error through an analogue of optical illusion. There are no such glitches in the system; so, such error does not undermine claims to introspective knowledge. Skepticism cannot gain a foothold from this source. But nor can it gain a foothold from such a source in the case of knowledge of other minds. There is thus no argument from illusion in the case of knowledge of other minds: we never have a visual impression as of a non-existent mental state in someone else that is qualitatively just like a veridical visual impression of a real mental state—because we have no such visual impression to start with. We don’t seem to see a mental state as we can seem to see a physical state. You might see a body in an illusory way if (say) it had a Muller-Lyer figure etched on it, but you don’t (can’t) see a mind in such an illusory fashion; you can’t say “It really looked to me exactly as if he believes the sky is green, but I know he doesn’t actually believe that”. You don’t and can’t hallucinate another mind—as it might be a zombie that strikes you visually as replete with consciousness. You might believe a zombie has a mind, but you don’t see it that way: for what would a visual impression of a mind be like? There are no optical illusions of the mind, as there are no optical illusions of number (seeing 2 as 3, say). Your knowledge of other minds cannot therefore be undermined by their possibility or frequency; skepticism cannot be advanced on this basis. So, in this respect, knowledge of other minds is better off than knowledge of other bodies. I know your mind better than I know your body (or my own), as a matter of principle.

Does this mean there is no sense in which you can see another mind? That doesn’t follow, given the elasticity of the concept of seeing. And it sounds perfectly reasonable to describe our knowledge of other minds in this way: I can see that you are upset or happy or confused. Seeing is not restricted to a certain subsystem of our visual sense—the subsystem that produces visual illusions. So, there is a type of seeing that is not prone to visual illusions. Knowledge of another mind can be seeing it (or involve this), only not the kind of basic seeing that is subject to optical illusion. The case is not like theoretical inference in which no one would say seeing is involved (atoms and the like). This, too, provides a bulwark against skepticism about other minds; now we have knowledge backed by seeing that is not vulnerable to perceptual illusion. Things are looking up for our knowledge of other minds; it seems better off than many kinds of human knowledge traditionally thought superior to it. Might it be one of our best types of knowledge? That is certainly a pleasant thought (“You really know me!”) and it is not far from phenomenological reality: for it really does seem that I am (sometimes) perfectly well aware of what is going on in your mind—I can know, for example, that you are enjoying yourself while playing tennis or boiling an egg. I can see that it is so, and I know that no visual illusion can be getting in the way. What more could you ask for as a situation conducive to knowledge?[1] It isn’t like being surrounded by constant optical illusions or actual blindness: I am in the (or a) seeing relation to your mind, and I don’t have to worry about any malfunctioning in my visual system producing illusions. I am home free, epistemically. I can be quite smug about my knowledge of your inner life, not racked with epistemic anxiety. For I am using an illusion-proof visual faculty–unimprovable. Not so for physical objects; here I must contend with the vagaries of error-prone vision, the perpetual possibility of illusion and hallucination. I erroneously see objects as colored. LSD does a number on my sense of sight. I can’t even see when two short lines are the same length. No wonder the skeptic can attack my knowledge of physical reality, but he doesn’t have this resource in the case of my knowledge of other minds. I can therefore relax about this knowledge, secure in the knowledge that I will not be caught out by a processing error in my visual system. Nice![2]

[1] I am not ruling out other sources of skepticism such as lack of logical entailment—they are another story. But I do think the argument from illusions is one of the most potent and influential sources of skeptical doubt about our knowledge of the external world.

[2] Perceptual constancies provide a good illustration of the asymmetry I am drawing attention to. The brain must do a lot of work to cancel the effects of different sized retinal images in the perception of objects at varying distances, using various cues without which visual illusion would set in. But no such problem afflicts the perception of other minds: we don’t nurse a tendency to see minds as different sizes depending on their distance from our eyes, as we do in the case of heads. Nothing in the visual system is tugging us in the direction of falsely assigning different sizes to minds according to their distance. One might think that the human visual system is always on the brink of delivering false perceptions when it comes to physical objects, but not so for other minds.