### A Response to Neil deGrasse Tyson

In my critical thinking classes I caution my students from jumping too quickly truth. The reason for this is that philosophers have long known that discovering what is true and false in the world is exceptionally difficult. What Tyson, particularly in Cosmos, so often beautifully and movingly articulates is that very long and painful struggle of bringing to light truth wrestled from a dim and dogmatic universe—sparking to flame Sagan's candle in the dark. There is incontrovertible nobility in discovering truth, and the great power of science is that it is undeniably a boundless engine of discovery. Yet even the most casual observer of science must admit, the road to truth is a very long journey—one that is hardly complete, and may not even be completable. To avoid being stuck, unable to discuss anything until it is proven true or false, philosophy has another set of tools at its disposal. For, prior to asking my students to consider truth, I ask them to consider if an argument even makes sense: if the pieces fit together, if there are strange gaps, if it takes certain assumptions for granted, if it assumes what it is trying to prove, etc. Perhaps one of the most important tools when thinking about an argument is this: if a given line of reasoning—when applied to similar situations—has a desirable result or leads to conclusions that are unacceptable. The contribution of logic and analysis is, in my belief, the great role of philosophy. So it has been with some surprise that I have watched so many of my philosophical colleagues jump directly to attempting to prove Tyson wrong rather than ask the more primary question: does Tyson's argument work?

It seems that Tyson's major complaint with philosophy is that it is an exercise in drawing conclusions from the a priori armchair. The complaint being that philosophy does not seem to directly measure or acquire information from the world, but instead draws conclusions from deductive, rationalistic, non-empirical means. The message Tyson conveys, again and again, is that dreaming up and pondering these sorts of questions from the armchair is a futile or perhaps even dangerous endeavor. The scientist, Tyson so often asserts, dreams up worldly questions and sets about to answer them.

The obvious problem with Tyson's position that the armchair is useless is that it not only makes philosophy obsolete, but it fundamentally eliminates wide swaths of mathematics and science as well. For mathematics—what Galileo called "the language in which science is spoken"—is deductive reasoning at its most pure. If such reasoning is, as Tyson asserts, navel-gazing, then none stare more intently than does the mathematician. Yet, what begins its life as armchair questioning often becomes highly useful to the scientist: binary numbers, number theory, Lie groups, complex numbers, quaternions, (and on the list could go). Each was once the byproduct of deductive work of mathematicians sitting quite comfortably in armchairs. While the synergy of mathematician and scientist is complex and many mathematicians make direct contributions to physics (and vice versa) surely at least some "pure" mathematicians have, perhaps long after their deaths, contributed to science, and they did so from a priori questions of the sort Tyson seems to dismiss. The great defender of pure mathematics, G. H. Hardy claims that James Clerk Maxwell and Albert Einstein, often taken as giants of science, are best understood as pure mathematicians—in other words, card-carrying navel gazers. Indeed, even G. H. Hardy's own mathematical efforts, believed utterly useless to "real world" problems, became a backbone of Niels Bohr's early formations of quantum mechanics. Often mathematics only becomes useful several years after its formulation, so the charge of "what has philosophy done for us lately?" seems uncomfortably applicable to pure mathematics as well. Physicists so often rely on the rationalistic fruits of mathematicians' armchair labors. If rationalistic, non-empirical, deductive inquiry is categorically useless, then it seems most of mathematics must be judged as such. This result strikes me, and I imagine most, as odd.

Even if Tyson is willing to concede that much of mathematics is mere navel gazing, and it is the scientist that, though empirical modeling, makes real the mathematicians ethereal musings, it nevertheless seems that doubling down on the uselessness of the a priori remains problematic. I fear that this position leads to the kind of science denial that Tyson spends so much of his career combatting. Within the sciences, particularly physics, a long tradition of theory exists. Even if one were to reject Hardy's categorization and move Maxwell and Einstein back to the physicist camp, one would be hard pressed to explain these scientists thinking as empirical—at least in their time. So often, particularly given the expense of doing science, science begins as a thought experiment—an armchair endeavor. The story of the neutrino, elegantly told in a recent episode of Cosmos, is an example of this. A great truth of the world seems to be that energy is conserved, that is, energy cannot be created or destroyed. Yet, upon doing very precise measurements of beta decay, Wolfgang Pauli noted that there seemed to be energy missing—seemingly violating the conservation of energy. Pauli concluded there must be an immensely small hitherto undetected particle to account for the missing energy. This particle was named 'neutrino' by Enrico Fermi meaning "little one." What is astonishing is that Pauli's assertion of the particle is seemingly contrary to his actual observations. All his instruments told him that there was energy missing. Quantum mechanics is filled with examples of classical physics being upended, it was not unreasonable to assume conservation may be another aspect of the Newtonian world but not the quantum one. Despite the facts on the ground and for purely rationalistic and deductive reasons, Pauli drew the conclusion that the there must be a very small undetected particle there. This result comes from the armchair—an armchair in a laboratory, but an armchair nevertheless. The astounding and unfathomable beauty and power of science is the interplay of real world testing and abstract postulating: the roles of the experimentalist and the theorist. To see this tension play out, one need only look to Tyson and Brian Greene's disagreements over string theory.

What is, to me, so troubling is that if Tyson's attacks are accurate then they not just hobble philosophy, but effectively strike a fatal blow to mathematics and even Tyson's beloved physics. It is as if in order to eliminate a cluttered desk, he has burnt his house to its foundation. The desk is assuredly less cluttered, but a great deal too much has been destroyed in the process. Strong critiques of philosophy (along the lines of those purposed by Tyson) exist and are frequently put forward by philosophers and others, but Tyson's argument is not one such critique.