Макс Тегмарк - Life 3.0 - Being Human in the Age of Artificial Intelligence

This physics perspective leads to three separate hard questions about consciousness, as shown in figure 8.1. First of all, what properties of the particle arrangement make the difference? Specifically, what physical properties distinguish conscious and unconscious systems? If we can answer that, then we can figure out which AI systems are conscious. In the more immediate future, it can also help emergency-room doctors determine which unresponsive patients are conscious.

Second, how do physical properties determine what the experience is like? Specifically, what determines qualia, basic building blocks of consciousness such as the redness of a rose, the sound of a cymbal, the smell of a steak, the taste of a tangerine or the pain of a pinprick? *2

Third, why is anything conscious? In other words, is there some deep undiscovered explanation for why clumps of matter can be conscious, or is this just an unexplainable brute fact about the way the world works?

The computer scientist Scott Aaronson, a former MIT colleague of mine, has lightheartedly called the first question the “pretty hard problem” (PHP), as has David Chalmers. In that spirit, let’s call the other two the “even harder problem” (EHP) and the “really hard problem” (RHP), as illustrated in figure 8.1. *3

Is Consciousness Beyond Science?

When people tell me that consciousness research is a hopeless waste of time, the main argument they give is that it’s “unscientific” and always will be. But is that really true? The influential Austro-British philosopher Karl Popper popularized the now widely accepted adage “If it’s not falsifiable, it’s not scientific.” In other words, science is all about testing theories against observations: if a theory can’t be tested even in principle, then it’s logically impossible to ever falsify it, which by Popper’s definition means that it’s unscientific.

So could there be a scientific theory that answers any of the three consciousness questions in figure 8.1? Please let me try to persuade you that the answer is a resounding YES!, at least for the pretty hard problem: “What physical properties distinguish conscious and unconscious systems?” Suppose that someone has a theory that, given any physical system, answers the question of whether the system is conscious with “yes,” “no” or “unsure.” Let’s hook your brain up to a device that measures some of the information processing in different parts of your brain, and let’s feed this information into a computer program that uses the consciousness theory to predict which parts of that information are conscious, and presents you with its predictions in real time on a screen, as in figure 8.2. First you think of an apple. The screen informs you that there’s information about an apple in your brain which you’re aware of, but that there’s also information in your brainstem about your pulse that you’re unaware of. Would you be impressed? Although the first two predictions of the theory were correct, you decide to do some more rigorous testing. You think about your mother and the computer informs you that there’s information in your brain about your mother but that you’re unaware of this. The theory made an incorrect prediction, which means that it’s ruled out and goes in the garbage dump of scientific history together with Aristotelian mechanics, the luminiferous aether, geocentric cosmology and countless other failed ideas. Here’s the key point: Although the theory was wrong, it was scientific ! Had it not been scientific, you wouldn’t have been able to test it and rule it out.

Someone might criticize this conclusion and say that they have no evidence of what you’re conscious of, or even of you being conscious at all: although they heard you say that you’re conscious, an unconscious zombie could conceivably say the same thing. But this doesn’t make that consciousness theory unscientific, because they can trade places with you and test whether it correctly predicts their own conscious experiences.

Figure 8.2: Suppose that a computer measures information being processed in your brain and predicts which parts of it you’re aware of according to a theory of consciousness. You can scientifically test this theory by checking whether its predictions are correct, matching your subjective experience.

On the other hand, if the theory refuses to make any predictions, merely replying “unsure” whenever queried, then it’s untestable and hence unscientific. This might happen because it’s applicable only in some situations, because the required computations are too hard to carry out in practice or because the brain sensors are no good. Today’s most popular scientific theories tend to be somewhere in the middle, giving testable answers to some but not all of our questions. For example, our core theory of physics will refuse to answer questions about systems that are simultaneously extremely small (requiring quantum mechanics) and extremely heavy (requiring general relativity), because we haven’t yet figured out which mathematical equations to use in this case. This core theory will also refuse to predict the exact masses of all possible atoms—in this case, we think we have the necessary equations, but we haven’t managed to accurately compute their solutions. The more dangerously a theory lives by sticking its neck out and making testable predictions, the more useful it is, and the more seriously we take it if it survives all our attempts to kill it. Yes, we can only test some predictions of consciousness theories, but that’s how it is for all physical theories. So let’s not waste time whining about what we can’t test, but get to work testing what we can test!

In summary, any theory predicting which physical systems are conscious (the pretty hard problem) is scientific, as long as it can predict which of your brain processes are conscious. However, the testability issue becomes less clear for the higher-up questions in figure 8.1. What would it mean for a theory to predict how you subjectively experience the color red? And if a theory purports to explain why there is such a thing as consciousness in the first place, then how do you test it experimentally? Just because these questions are hard doesn’t mean that we should avoid them, and we’ll indeed return to them below. But when confronted with several related unanswered questions, I think it’s wise to tackle the easiest one first. For this reason, my consciousness research at MIT is focused squarely on the base of the pyramid in figure 8.1. I recently discussed this strategy with my fellow physicist Piet Hut from Princeton, who joked that trying to build the top of the pyramid before the base would be like worrying about the interpretation of quantum mechanics before discovering the Schrödinger equation, the mathematical foundation that lets us predict the outcomes of our experiments.

When discussing what’s beyond science, it’s important to remember that the answer depends on time! Four centuries ago, Galileo Galilei was so impressed by math-based physics theories that he described nature as “a book written in the language of mathematics.” If he threw a grape and a hazelnut, he could accurately predict the shapes of their trajectories and when they would hit the ground. Yet he had no clue why one was green and the other brown, or why one was soft and the other hard—these aspects of the world were beyond the reach of science at the time. But not forever! When James Clerk Maxwell discovered his eponymous equations in 1861, it became clear that light and colors could also be understood mathematically. We now know that the aforementioned Schrödinger equation, discovered in 1925, can be used to predict all properties of matter, including what’s soft or hard. While theoretical progress has enabled ever more scientific predictions, technological progress has enabled ever more experimental tests: almost everything we now study with telescopes, microscopes or particle colliders was once beyond science. In other words, the purview of science has expanded dramatically since Galileo’s days, from a tiny fraction of all phenomena to a large percentage, including subatomic particles, black holes and our cosmic origins 13.8 billion years ago. This raises the question: What’s left?