Theoretical Physicist David Deutsch on the limitations of science

One of the most important limits of science is that it isn't philosophy. [...] Scientism is the purported application of science to problems that are really philosophical. Such as the question of whether animals really feel pain or not. We can tell whether animal's nerves are excited and whether their brains react to that. But whether an animal feels pain in the sense that humans do, or merely react in the sense that a robot does, that is ultimately a matter of philosophy, because it's only philosophy that can determine the criterion for science to use when trying to distinguish between those cases. So that's a limit of science--trying to reach into philosophy is scientism. [...] I would say to [those who claim that the only good explanations are scientific explanations] that that theory is not part of science, and therfore it rules itself out.

Taken from an interview with Robert Lawrence Kuhn.

How to (really) think about metaphysics

Today I was visiting some of the blogs I frequent and I stopped by the blog Atheism and the City, authored by a frequent commenter at my blog who goes by the name “The Thinker”.  He has just posted a review of Chapter 3 of Edward Feser’s book The Last Superstition. There is much to quibble with in Thinker’s post, but I’ll save an attempted refutation of his arguments for another day. My main focus here is regarding his comments on metaphysics and scientism.  I’ve gone on ad nauseum on this blog about the importance of metaphysics, and the falsity and self-refutation of scientism (see here),  but Thinker presents a different spin on this issue—a view he calls “weak scientism”—and therefore I felt the need to point out its falsity, thereby tossing it in the trash-bin with the other failed metaphysical frameworks.

Thinker begins to articulate his thoughts on weak scientism:

 I hold to what is sometimes called "weak scientism." Unlike strong scientism, which says that "the characteristic inductive methods of the natural sciences are the only source of genuine factual knowledge and, in particular, that they alone can yield true knowledge about man and society," weak scientism says that the natural sciences are given a privileged status over metaphysics and logic and all other methods of derived knowledge, but it stops short of saying that science and logic are the "only" ways of yielding true knowledge.

It’s hard to say exactly what Thinker means by the natural sciences entertaining a “privileged status” over metaphysics and logic. Perhaps he means that the natural sciences are more genuine and pure methods for attaining knowledge of reality. It is certainly true that the natural sciences have illumined the majority of beliefs and knowledge that we have about how the natural world behaves. But does this give one warrant to claim that science therefore entertains a privileged status for gaining knowledge about reality, over and above metaphysics? I don’t see how. For, as I’ve argued before, science tells us how the world behaves, but it does not, and cannot, tell us why—only metaphysics can hope to do this. Science might be able to tell us about the four forces of nature, for example, but it cannot tell us why those forces obtain at all as opposed to others. So I fail to see how science should be given a privileged status regarding methods of inquiry above methods like metaphysics.

The Thinker continues:

Furthermore, I apply this privileged status of science mostly when entertaining questions regarding ontology, such as the fundamental nature of reality—for which science is our most reliable epistemology, contrary to what Feser says.

So now Thinker says that science seems to be our most reliable guide for answering questions regarding the fundamental nature of reality. Again, this presents a couple problems. First, science by itself does not have the tools to comment on the fundamental nature of reality. This might seem like an arrogant statement against science, but it’s the truth. Scientific law only describes what already exists and how it behaves. But simply describing what already exists is purely abstract, in that it doesn’t actually enlighten us to the intrinsic nature of what it’s describing. So science simply doesn’t cut deep enough to penetrate the fundamental nature of reality.

Second, the natural sciences necessarily describe only the natural world. Therefore, if there were other aspects of reality, science could not enlighten us one way or another regarding their behavior. In fact, even if there exists no supernatural aspects of reality, science could likewise not comment on its non-behavior. The point is that science is completely silent on the question of what comprises the set of reality and being. To construct my point in another fashion, the description of a set of elements is not sufficient to conclude that only the set exists. Something else would be needed to ground this proposition, and it couldn’t be a mere description of a set’s behavior.

Let’s move on:

No logician could ever derive the physics of quantum mechanics from the laws of logic, or from metaphysics. Only empirical evidence could enlighten us to such phenomena, and the universe is ultimately quantum mechanical in nature.

Thinker continues to make the similar mistakes here. First, I agree that science, and only science, enlightens us to the physics of quantum mechanics and general relativity etc. But nobody ever said that metaphysics was the method of inquiry that should have done this. You see, science uncovers the physical contingencies of the universe that can be repeated and predicted using abstract mathematical equations—equations that could have been different. But, metaphysics enlightens us to the necessities of the universe, and anything that could or would exist. It tells us the ontology of causality, identity, first principles, time and free will etc. So, to once again engage in chest-thumping on behalf of science because of its discoveries of the physical contingencies of the world is simply misplaced here, since metaphysics wasn’t attempting to do this in the first place. It’s like a basketball player praising his dunking ability, while playing soccer. Metaphysics tells us the fundamental nature of reality, and science tells us how this reality happens to behave. The latter is not equivalent to the former.

Second, Thinker shoots himself in the foot here with his last statement about the universe being quantum mechanical in nature. How does he know the universe is entirely quantum mechanical in nature? Well quantum mechanics cannot tell him this, since, to reiterate, QM is only a description of sub-atomically existing matter. How does he know this description constitutes the fundamental nature of reality? Even if he has an answer to this question, it will not be given to him by QM. He will have to have some other fulcrum to lay this proposition upon. And this goes for any set of natural sciences you want to erect as the end-all be-all description of reality. A description of a set simply will not be sufficient for concluding that only what’s in the set is what exists, or that the set does not have an aspect of its nature not captured by the original description. The Thinker’s attempt, then, to ground weak scientism seems to have failed.