The mind-world similarity thesis

Eventually, the modern tradition becomes very suspicious the idea that there can be a similarity between the contents of the mind and characteristics of things in the external world. First, we have Locke denying the possibility of the similarity thesis for secondary qualities like red and sweet, and then we have others, like Berkeley and Reid, denying the possibility of the similarity thesis for primary qualities, like triangularity. In the case of primary qualities, it just seems absurd to think that the mind should hold something like a triangle.

This denial of the possibility of the similarity thesis seems to me to be a massive failure of the philosophical imagination, and a neglect of a sympathy to the history of philosophy. The allegation of the absurdity of thinking that triangularity should be present in the mind and in the world seems to come from thinking that the only way triangularity can be present in an entity is by the entity’s having triangularity. But why should having be the only possible relation by which triangularity could be present in a thing?

Here are some ways in which a property could be in a thing without the thing having the property.

• Let S be the set of the polygonality properties. Thus, the members of S are triangularity, quadrilaterality, etc. Triangularity is then in S qua member of S, but S is not a triangle—it does not have triangularity.

• On divine simplicity, God is identical with his divinity. But God can be present in Francis without Francis having God’s divinity—i.e., without Francis being divine.

• Suppose that I have a wood triangle in a steel box. The triangle’s triangularity is in the triangle, and the triangle is in the box, so the triangularity is in the box.

• Say that my fingernail is pointy. The properties of a thing are parts of a thing. So, the fingernail has its pointiness as a part. But the fingernail is a part of me, and parthood is transitive. So the pointiness of the fingernail is a part of me. But I am not pointy, even though I have a pointiness in me.

There is nothing absurd, then, about there being triangularity in the mind without the mind being itself triangular.

Moreover, having triangularity in the mind is not even a necessary condition for there to be a relevant similarity between the mind and a wooden triangle outside of me. It could be that the triangularity in the triangle is not a simple entity, but is composed of two components, T and P, where the P component is common (either as type or as token) between all properties, and the T component distinguishes triangularity from other properties. Thus, squareness might consist of S and P, and redness might consist of R and P. Well, then, we can suppose that when I think of or perceive a triangle as a triangle, then T comes to be in my mind without P doing so. Perhaps T comes to be “elementally” present in my mind, or perhaps it comes to be compounded with something else. (Here is a Thomistic version: triangularity has an essence T and a natural esse P; when present in the mind, the essence is there, but instead comes to have a different thing from the natural esse, say an intentional esse.) In either case, we have something importantly in common between the mind and the triangle qua triangular, namely T, without having triangularity in the mind, but only a component of triangularity.

There is no paucity of options. Indeed, we have an embarrassment of riches—many, many ways of making the similarity thesis true.

Retinal images

Here's a nice way to get an idea just how much processing intervenes between retinal images and conscious perception. Unless you're reading this post through a screen reader or some other assistive technology, while you're reading the post, your eyes are moving in very fast saccades. So your retinal images are a mess. They are like a video produced by a camera that is waving around apparently randomly at high speed. But screen and the text on it looks to you as if it was basically still. You do not see the mess of retinal images with different orientations—they are all stitched together in complex post-processing into an image of something unmoving. Now, walk around while looking at some three solid and unmoving dimensional object in your environment. In addition to the shifts in retinal image produced by the eye motion, there are shifts due to head motion, due to the up-and-down rhythm of your walk, as well as the exposures of hidden surfaces. Yet the solid and unmoving object looks unmoving.

Of course, there are times when the post-processing fails—there are illusions of motion. For instance, because there is a background behind the laptop screen, and parallax ensures apparent relative movement of the laptop and the background, when I move my head, it does look like the laptop is moving relative to the background.

In any case, what we see does not look like what you get from a head mounted camera. And our retinal images are even jumpier than that, as the head mounted camera does not follow the eye-muscle saccades. We have some really quite amazing image stabilization.

Colors

One might think that all there is to an object's being red is that object's appearing red to one in standard circumstances. Here is a potential counterexample. I gave my four-year-old son some red gelatin dessert (probably not of the Jell-O brand) and asked him what color it was. He said: "It looks red" (his slight emphasis). Now, he wasn't expressing a doubt about whether the circumstances were standard. Rather, because he is red-green colorblind, he knows there is a gap between an object's appearing red to him in standard circumstances, and its actually being red. (He agreed later that it looked "reddish green" to him. But once I told him that it was actually reddish orange, he accepted that, and from then on was very firm that it was reddish orange.) I suppose "standard circumstances" could include "standard observer", in which case there is no counterexample. In any case, the point here is that color terms for my son have a serious intersubjectivity, and perhaps objectivity, to them.

Interestingly, I think that occasionally my son bridges this gap inferentially—the object looks more like red objects do than like green objects do, so it's probably red—and sometimes he bridges it non-inferentially through an internalization of stereotyped colors. Thus, when asked about a green leaf or green grass what color it is, he instantly responds that it's green—I think he may be seeing it as green in the way in which I can see a person as old. Does he have the quale of green in the case of the green leaf or green grass, when he sees it (visually!) as green? I have no idea. If to have a quale of green is just to be non-inferentially visually appeared to greenly, then he does, since he is visually appeared to greenly, except that in his case the green appearance of the leaf depends also on shape. If the green appearance depends also on shape, it's hard to say that it has the quale of green. But maybe it does. (Suppose I heard an object as green—maybe because I could hear the molecules vibrating as they reflect green light—would that have the same quale as seeing it as green?)