Mentalese

It took Alan Turing, the brilliant British mathematician and philosopher, to make the idea of a mental representation scientifically respectable. Turing described a hypothetical machine that could be said to engage in reasoning. In fact this simple device, named a Turing Machine in his honor, is powerful enough to solve any problem that any computer, past, present, or future, can solve. And it clearly uses an internal symbolic representation – a kind of mentalese – without requiring a little man or any occult processes. By looking at how a Turing machine works, we can get a grasp of what it would mean for a human mind to think in mentalese en.wikipedia.org/wiki/Language_of_thought_hypothesis as opposed to English.

In essence, to reason is to deduce new pieces of knowledge from old ones. A simple example is the old chestnut from introductory logic: if you know that Socrates is a man and all men are mortal, you can figure out that Socrates is mortal. But how could a hunk of matter like brain accomplish this feat? The first key idea is a ‘representation’: a physical object whose parts and arrangement correspond piece for piece to some set of ideas or facts. For example the pattern of in on this page

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Socrates isa man

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is a representation of the idea that Socrates is a man. the shape of one group of ink marks, Socrates, is a symbol that stands for the concept of Socrates. The shape of another set of ink marks, isa, stands for the concept of being an instance of, and the shape of third, man, stands for the concept of man. Now, it is crucial to keep one thing in mind. I have put these ink marks in the shape of English words as a courtesy to you, the reader,

so that you can keep them straight as we work through the example. But all that really matters is that they have different shapes. I could have used a star of David, a smiley face, and the Mercedes Benz logo, as long as I used them consistently.

Keeping these conventions in mind, now imagine that the page has a second west of ink marks, representing the proportion that every man is mortal:

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Socrates isa man
Every man ismortal

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To get reasoning to happen, we now need a ‘processor’. A processor is not a little man (so one needn’t worry about an infinite regression of homunculi inside homunculi) but something much stupider; a gadget with a fixed number of reflexes. A processor can react to different pieces of a representation and so something in response, including altering the representation or making a new ones. For example, imagine a machine that can move around on a printed page. It has a cutout in a shape of the letter sequence isa, and a light sensor that can tell when the cutout is superimposed on a set of ink marks as the exact shape of the cutout. The sensor is hooked up to a little pocket copies, which can duplicate any set of ink marks, either by printing identical ink marks somewhere else on the page or by burning them into a new cutout.