by Jochen Szangolies

Whenever I use words like ‘reality’, ‘truth’, or ‘existence’, I feel an almost irresistible urge to mark my vague sense of unease by liberal application of scare quotes. After all, what could such words even mean? They seem to denote concepts too vast and simultaneously slippery to be pinned down by a simple denotative term. Like trying to point at everything all at once, such terms seem to cast so wide a net that they fail to single out any one thing in particular.

There is, I think, a good reason for this unease, and modern science is beginning to reveal the contours of it—and with that, some of its own limitations. In the previous column, I have argued that the typical starting point for science, conventionally understood, is the existence of an independent world that we can approximate ever more closely in our knowledge of it. There is a subject-object distinction baked into it that delineates this process neatly into questions of epistemology, of what we can know and how we can know it, and ontology, of what there is. According to this story, a subject with the right epistemological tools can uncover the objective ontology of the world through patient and painstaking labor, perhaps never fully getting there, but coming arbitrarily close. Such, at least, seems to be the hope.

That prior column ended with a discussion of the Kochen-Specker theorem, a famous result in the foundations of quantum mechanics that essentially entails that, when it comes to the (allegedly) microscopic realm subject to the laws of quantum physics, the above clear delineation is not possible in general. What we find must, to some extent, depend on how we look—the ontological inventory of the world is not independent from the epistemic process of interrogating it. Values of observable quantities, if they exist at all, must be contextual, that is, depend on what other values are queried simultaneously.

For the macroscopic world, this strikes us as an absurdity: the color of a ball, say, should not depend on whether it is simultaneously measured together with its size, or its weight! And in our everyday experience, where in principle all quantities can be observed simultaneously, no such effects occur. So perhaps this is just the quantum world being, you know, weird? Maybe for all practical purposes, we can still rely on the world being a solid bedrock of facts awaiting our discovery, like pill bugs hiding under so many rocks to be turned over? Read more »