“I am a passionate scientist who is passionate about science, but I also think scientism is a huge mistake”, writes Adam Frank, an astrophysicist at the University of Rochester, in an article in The Big Think. As another astrophysicist, who has called this blog “defending scientism”, I am inspired to reply.

Adam Frank, Professor of Astrophysics and advocate of science.
Such disputes can boil down to what one means by the word “scientism”. Professor Frank quotes one definition as “the view that science is the best or only objective means by which society should determine normative and epistemological values”. On that definition I also would reject scientism (indeed I don’t think that anyone does advocate that position). Science cannot prescribe values or aims. Science is descriptive, not prescriptive, it gives you knowledge, not normativity (instead, values, aims and normativity can only come from humans).
But Frank also expounds:
In the philosophy that would come to underpin scientism, “objective” came to mean something more like “the world without us.” In this view, science was a means of gaining access to a perfectly objective world that had nothing to do with humans. It gave us a “God’s eye view” or a “perspective-less perspective.” Science, according to this philosophy, revealed to us the “real world,” which was the world independent of us. Therefore, its truths were “deeper” than others, and all aspects of our experience must, eventually, reduce down to the truths that science reveals. This is scientism.
I’m close to agreement with this version of scientism. Science does indeed attempt to reveal a real, objective world that is independent of us, and to a large measure it succeeds (though we can never attain any absolute certainty). And yes, science does give us truths about the world (as best as we humans can access them) that are more reliable and more extensive and thus “deeper” than other attempts to describe the world. But no, it is not true that “all aspects of our experience must, eventually, reduce down to the truths that science reveals”. Science is solely about attaining the best and truest description of the world (which includes ourselves) that we can. It doesn’t even pretend to encompass “aspects of our experience” other than that (indeed I’m not even sure what this claim would mean, and, again, I don’t think this is a view that anyone actually holds).
Professor Frank’s objection to scientism is that:
[Scientism] is just metaphysics, and there are lots and lots of metaphysical beliefs […] that you can adopt about reality and science depending on your inclinations. […] Scientism claims to be the only philosophy that can speak for science, but that is simply not the case. There are lots of philosophies of science out there.
So, according to Frank, scientism is just metaphysics, there is no evidence for it, and so adopting it comes down to personal choice, the very opposite of science. Effectively, science does not point to scientism.
I don’t find this critique convincing. In essence, “scientism” is a unity-of-knowledge thesis that the real world is a seamless, self-consistent whole, and thus that the best description of it will also be (or should, at least, aim towards being) a seamless, self-consistent whole. That is, there should be a “consilience”, or self-consistent meshing of different areas of knowledge and of ways of attaining that knowledge. Scientism is a rejection of the idea that there are distinct and different “ways of knowing”, each appropriate to different and distinct “domains” of knowledge.
But is that claim only a metaphysical belief, whose adoption is merely a “faith”? I submit that, no it is not. Instead, it’s the product of doing science and seeing what works best. Science rejects the supernatural, not as an a priori commitment, but because models of reality work better without it. In medieval times “the heavens” and the earthly world were regarded as different domains to which different rules applied, but then Newton invented a law of gravity that applied both to the Earth-bound fall of an apple and to the orbit of the Moon, unifying the two domains. Even then, the worldview of a scientist could involve a God (invoked by Newton, for example, to keep planetary orbits stable), but, as science progressed, it was found that we “had no need of that hypothesis“. And it had been thought that living animals were utterly distinct from inanimate matter, but nowadays the disciplines of physics and chemistry transition seamlessly through “biochemistry” into the disciplines of biology and ecology. And any proper account of sociology needs to mesh with evolutionary psychology.
Through that progression we have found no sharp divides, no deep epistemological ravines that science cannot cross. The strategy of unifying different areas of knowledge has always proven the more successful.
Thus science does indeed point to scientism, and the unity-of-knowledge view is a product of science. It is not simply one of a number of un-evidenced metaphysical possibilities, it is the one to which the history and current trajectory of science points.
And the idea is refutable. If you want to reject scientism then put forward an alternative “way of knowing” that gives reliable knowledge about the world and yet is clearly distinct from the methods of science. Be sure to include a demonstration that such knowledge is indeed valid and reliable, and thus comparable to scientific knowledge, but without using science in that demonstration.