English physicist and mathematician Roger Penrose (born in 1931) took a different leap of faith in proposing the source of consciousness, though his also concerned the microtubules—specifically, their purported quantum computing abilities. His reasoning, although not explicitly stated, seemed to be that consciousness is mysterious, and a quantum event is also mysterious, so they must be linked in some way.
Penrose started his analysis with Turing’s theorems on unsolvable problems and Gödel’s related incompleteness theorem. Turing’s premise (which was discussed in greater detail in chapter 8) is that there are algorithmic problems that can be stated but that cannot be solved by a Turing machine. Given the computational universality of the Turing machine, we can conclude that these “unsolvable problems” cannot be solved by any machine. Gödel’s incompleteness theorem has a similar result with regard to the ability to prove conjectures involving numbers. Penrose’s argument is that the human brain is able to solve these unsolvable problems, so is therefore capable of doing things that a deterministic machine such as a computer is unable to do. His motivation, at least in part, is to elevate human beings above machines. But his central premise—that humans can solve Turing’s and Gödel’s insoluble problems—is unfortunately simply not true.
A famous unsolvable problem called the busy beaver problem is stated as follows: Find the maximum number of 1s that a Turing machine with a certain number of states can write on its tape. So to determine the busy beaver of the number n, we build all of the Turing machines that have n states (which will be a finite number if n is finite) and then determine the largest number of 1s that these machines write on their tapes, excluding those Turing machines that get into an infinite loop. This is unsolvable because as we seek to simulate all of these n-state Turing machines, our simulator will get into an infinite loop when it attempts to simulate one of the Turing machines that does get into an infinite loop. However, it turns out that computers have nonetheless been able to determine the busy beaver function for certain ns. So have humans, but computers have solved the problem for far more ns than unassisted humans. Computers are generally better than humans at solving Turing’s and Gödel’s unsolvable problems.
Penrose linked these claimed transcendent capabilities of the human brain to the quantum computing that he hypothesized took place in it. According to Penrose, these neural quantum effects were somehow inherently not achievable by computers, so therefore human thinking has an inherent edge. In fact, common electronics uses quantum effects (transistors rely on quantum tunneling of electrons across barriers); quantum computing in the brain has never been demonstrated; human mental performance can be satisfactorily explained by classical computing methods; and in any event nothing bars us from applying quantum computing in computers. None of these objections has ever been addressed by Penrose. It was when critics pointed out that the brain is a warm and messy place for quantum computing that Hameroff and Penrose joined forces. Penrose found a perfect vehicle within neurons that could conceivably support quantum computing—namely, the microtubules that Hameroff had speculated were part of the information processing within a neuron. So the Hameroff-Penrose thesis is that the microtubules in the neurons are doing quantum computing and that this is responsible for consciousness.
This thesis has also been criticized, for example, by Swedish American physicist and cosmologist Max Tegmark (born in 1967), who determined that quantum events in microtubules could survive for only 10−13 seconds, which is much too brief a period of time either to compute results of any significance or to affect neural processes. There are certain types of problems for which quantum computing would show superior capabilities to classical computing—for example, the cracking of encryption codes through the factoring of large numbers. However, unassisted human thinking has proven to be terrible at solving them, and cannot match even classical computers in this area, which suggests that the brain is not demonstrating any quantum computing capabilities. Moreover, even if such a phenomenon as quantum computing in the brain did exist, it would not necessarily be linked to consciousness.
You Gotta Have Faith
What a piece of work is a man! How noble in reason! How infinite in faculties! In form and moving, how express and admirable! In action how like an angel! In apprehension, how like a god! The beauty of the world! The paragon of animals! And yet, to me, what is this quintessence of dust?
The reality is that these theories are all leaps of faith, and I would add that where consciousness is concerned, the guiding principle is “you gotta have faith”—that is, we each need a leap of faith as to what and who is conscious, and who and what we are as conscious beings. Otherwise we could not get up in the morning. But we should be honest about the fundamental need for a leap of faith in this matter and self-reflective as to what our own particular leap involves.
People have very different leaps, despite impressions to the contrary. Individual philosophical assumptions about the nature and source of consciousness underlie disagreements on issues ranging from animal rights to abortion, and will result in even more contentious future conflicts over machine rights. My objective prediction is that machines in the future will appear to be conscious and that they will be convincing to biological people when they speak of their qualia. They will exhibit the full range of subtle, familiar emotional cues; they will make us laugh and cry; and they will get mad at us if we say that we don’t believe that they are conscious. (They will be very smart, so we won’t want that to happen.) We will come to accept that they are conscious persons. My own leap of faith is this: Once machines do succeed in being convincing when they speak of their qualia and conscious experiences, they will indeed constitute conscious persons. I have come to my position via this thought experiment: Imagine that you meet an entity in the future (a robot or an avatar) that is completely convincing in her emotional reactions. She laughs convincingly at your jokes, and in turn makes you laugh and cry (but not just by pinching you). She convinces you of her sincerity when she speaks of her fears and longings. In every way, she seems conscious. She seems, in fact, like a person. Would you accept her as a conscious person?
If your initial reaction is that you would likely detect some way in which she betrays her nonbiological nature, then you are not keeping to the assumptions in this hypothetical situation, which established that she is fully convincing. Given that assumption, if she were threatened with destruction and responded, as a human would, with terror, would you react in the same empathetic way that you would if you witnessed such a scene involving a human? For myself, the answer is yes, and I believe the answer would be the same for most if not virtually all other people regardless of what they might assert now in a philosophical debate. Again, the emphasis here is on the word “convincing.”