Neurosurgeon Michael Egnor: Why Machines Will Never Think

At the official launch of the Walter Bradley Center for Natural and Artificial Intelligence, July 11, 2018, neurosurgeon Michael Egnor offered some thoughts on artificial vs. natural intelligence. He sends us this piece, further developing some of his ideas:

A cornerstone of the development of artificial intelligence is the pervasive assumption that machines can, or will, think. Watson, a question-answering computer, beats the best Jeopardy players, and anyone who plays chess has had the humiliation of being beaten by a chess engine. (I lose to even the most elementary levels of the chess program on my iPhone). Does this mean that computers can think as well as (or better than) humans think? No, it does not. Computers are not “smart” in any way. Machines are utterly incapable of thought.

The assertion that computation is thought, hence thought is computation, is called computer functionalism. It is the theory that the human mind is to the brain as software is to hardware. The mind is what the brain does; the brain “runs” the mind, as a computer runs a program. However, careful examination of natural intelligence (the human mind) and artificial intelligence (computation) shows that this is a profound misunderstanding.

What is the hallmark of human thought, and what distinguishes thoughts from material things? Franz Brentano (1838–1917), a German philosopher in the 19th century, answered this question decisively. All thoughts are about something, whereas no material object is inherently “about” anything. This property of aboutness is called intentionality, and intentionality is the hallmark of the mind. Every thought that I have shares the property of aboutness—I think about my vacation, or about politics, or about my family. But no material object is, in itself, “about” anything. A mountain or a rock or a pen lacks aboutness—they are just objects. Only a mind has intentionality, and intentionality is the hallmark of the mind.

Another word for intentionality is meaning. All thoughts inherently mean something. A truly meaningless thought is an oxymoron. The meaning may be trivial or confusing, but every thought entails meaning of some sort. Every thought is about something, and that something is the meaning of the thought.

The hallmark of human thought is meaning, and the hallmark of computation is indifference to meaning. That is, in fact, what makes thought so remarkable and also what makes computation so useful. You can think about anything, and you can use the same computer to express your entire range of thoughts, because computation is blind to meaning.

What is the hallmark of computation? Computation is an algorithmic process. It is the matching of an input to an output according to an algorithm. That function is termed a Turing Machine. Computation in this sense is independent of the physical substrate on which it occurs. Computation can take place on silicon, copper, or protoplasm.

Yet computation is independent of the semantic content. For example, you can type a sentence containing the proposition ‘broccoli tastes good’ on your computer, using the hardware and software of your word-processing program. You can also type the proposition ‘broccoli tastes bad’ on the same computer and program. The computation is identical. The identical hardware and software are used to type the two propositions that have opposite meanings. You can photograph a bright sunny day and a dark starry night with the same digital camera. Your word processor and your digital camera are blind to meaning. The only meaning in computation is the meaning put into it, and extracted from it, by human minds. You don’t need a different computer or a different software to write essays that have different meanings or to take pictures of different scenes. Computation is indifferent to meaning.

The hallmark of human thought is meaning, and the hallmark of computation is indifference to meaning. That is, in fact, what makes thought so remarkable and also what makes computation so useful. You can think about anything, and you can use the same computer to express your entire range of thoughts because computation is blind to meaning.

Thought is not merely not computation. Thought is the antithesis of computation. Thought is precisely what computation is not. Thought is intentional. Computation is not intentional.

A reader may object at this point that the output of computation seems to have meaning. After all, the essay was typed on a computer. Yes, but all of the meaning in the computation is put into it by a human mind. Computation represents thought in the same way that a pen and paper can be used to represent thought, but computation does not generate thought and cannot produce thought. Computation can, of course, distort thought, reveal thought, conceal thought, etc., just as pen and paper can. And that is the challenge we face in understanding how artificial intelligence works and how it will affect us.

But to believe that machines can think or that human thought is a kind of computation is a profound error. Belief in this fundamental error about AI will lead us away from, not toward, the truth about AI. Machines, for example, will never become malevolent and harm mankind. Men will act with malevolence, using machines, or men will use machines in ways that (unintentionally) harm others. Men can use cars malevolently and carelessly and can thus harm others. But the malevolence and careless is in the man, not in the car.

To paraphrase Pogo: we have met AI, and AI is us.