Does the human mind perceive sight in 3 dimensions, or do we actually see in 2 dimensions, where depth perception and distance really don't exist in our mind? For example, I am looking at a bridge 100 yards away, I place my finger directly in front of the bridge. Now in the external world there exists a finger an arm's length away from my eyes, and a bridge 100 yards away. If the picture that occurs in my mind is a 2 dimensional picture then my finger and the bridge are located on the same plane in my mind, and distance would not truly exist in my perception. But if the mind's perception of sight occurs in 3 dimensions, like a hologram, then the picture I receive through sight must occur in a three dimensional space in my mind, where distances must be in the same but smaller ratios as exist in the external world. Here occurs a problem. If our perception of vision occurs in smaller but equal ratios of three dimensions, then the same object would have two sizes: That which exists in my mind (extremely small), and that which exists in the external world (large). Since the same object cannot possibly exist as both small and large, then we are back to the 2 dimensional version of sight where distance and depth do not exist. This was hard to put into words, but I hope someone can help me out. Billy H.

We need to keep some things straight here. The "picture" that occurs in your mind, if there is such a thing, is a representation. You don't have a single object, the bridge say, which has two sizes. The bridge isn't both in the external world and in your mind. It's just in the external world. If there is a "picture" of the bridge in your mind, then it is a picture of the bridge, not the bridge, and the fact that it has a different size from the bridge is hardly surprising.

More generally, whether the representation is three-dimensional or not (and there is some empirical evidence that it is, actually) has nothing particular to do with whether it is capable of representing three dimensions. Think of a map. On the map, dots represent towns and the relative distances between little dots represent distances. If it's a topographic map, then there may be lines that represent height. The map represents three dimensions even though it is essentially two dimensional.

It's important to be clear here that you do not see the picture in your mind, though, the way you see the map. What you see is the bridge, and you see it three-dimensionally by having some representation of it in your mind, and that representation represents something three-dimensional.

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