Common Sense Scientific Realism

Reference Material:
Scientific Realism – SEP (Anjan Chakravartty)
Scientific Realism – Stathis Psillos

        This post continues my foray into the philosophy of science. I’m zooming out from the previous post, a more in-depth look at Kuhn’s Structure of Scientific Revolutions, to view the landscape of the philosophy of science more broadly. In particular, I want to consider a collection of perspectives generally known as scientific realism. My approach will be somewhat in the style of my posts on emergence – I’ll make reference to existing philosophical work (as I did here), but I want to develop my own views at least somewhat independently (similar to here), perhaps at the risk of redundancy or naivete. So here we go.
        To start, what is meant by scientific realism? In this post, I’ll be working with the 3-part description outlined by Chakravartty in the SEP article (and echoed by Psillos [xix]). Scientific realism is generally advocating a realist position in three different dimensions. Metaphysically, scientific realism asserts the existence of a mind-independent reality (as opposed to, most prominently, idealism). Semantically, scientific realism takes scientific claims at face-value (as opposed to interpreting them purely instrumentally). And epistemologically, scientific realism holds that the theoretical claims of scientific theories give us knowledge about the world (as opposed to more skeptical interpretations).
        To make the discussion of scientific realism more concrete, I want to work with a specific scientific claim as an example. Let’s take Richard Feynman’s proposal for the scientific statement containing the most information in the fewest words – “all things are made of atoms”, or perhaps more bluntly, “atoms exist” (disposing, for current purposes, of the claim that atoms make up everything, and settling for something). What does this claim mean when interpreted from the viewpoint of scientific realism? Metaphysically, it means that atoms exist independent of our minds. They exist when we’re not thinking about them, when we’re not looking at them, in places we’ve never been and will never go. Semantically, it means that atoms really do exist. By ‘really’, I mean what J. J. C. Smart (Psillos [236]) means – the ‘really’ is meant to distinguish the existence of atoms from the nonexistence of things like logical constructions (e.g. average height) and fictional objects (e.g. unicorns). Sure, these entities exist in some sense – you can compute the average height, and there are stories about unicorns. But they don’t really exist, out there in the actual world (note the reliance on the metaphysical dimension). And epistemologically, a realist interpretation is that modern scientific theories, accompanied by the relevant empirical evidence, justify the claim that atoms exist.
        I want to restate this realist interpretation of the claim “atoms exist” in as plain a way as possible. The restatement takes the form of an analogy or comparison. What the scientific realist means by “atoms exist” is something like – atoms exist, in just the same way that chairs exist (chairs exist independent of our minds, they really do exist, and we’re justified in claiming their existence). What does this amount to? When we say chairs exist, we mean, for starters, that there are objects in the world that look a certain way, i.e. cause light to reflect off of them such that they look like, well, chairs. They also satisfy a bunch of other conditions: I can sit on them, I can pick them up and move them, they hurt my shins when I run into them in the dark, I could chop one up and burn it, etc. So when I say chairs exist, I say everything that chairs do (or potentially do), every way in which they can interact (or potentially interact) with their surroundings, and then claim that there are objects in the world that do all those things and interact in all those ways. In other words, there is nothing to chairs existing over and above the actual instantiation of all their effects (see Psillos [155-6]). I think the realist interpretation of “atoms exist” should be analogous. We describe everything that atoms do, and then go out and observe all those effects, and that’s what we mean by “atoms exist”. There is nothing deeper left to say about their existence. What the scientific realist means by “atoms exist” is no more unusual or exotic than what any person means by “chairs exist”.
        But there is a huge difference between chairs and atoms that makes this analogy seem strained – we can plainly see chairs, whereas we can’t see atoms, as such. This point is the observable/unobservable distinction that is so central to discussions of scientific realism (the words appear a combined 73 times in the SEP entry). While there are good arguments that this distinction is actually incoherent (Psillos [199]), let’s take it as is for the sake of argument. I want to extend the analogy with chairs to try to motivate the idea that this distinction shouldn’t prevent us from claiming that atoms exist in the same everyday way we do for chairs. This will take the form of 4 scenarios (I know they’re strange, bear with me).
  • Scenario 1: The world is exactly as it is today.
  • Scenario 2: Same as scenario 1, except all chairs are invisible. They are like normal chairs in every other respect.
  • Scenario 3: Scenario 2, but in the past, before chairs were “discovered”. There are reports coming in of people banging their shins on mysterious invisible objects, being able to sit at tables in a novel way, etc.
  • Scenario 4: Scenario 3, but include some noise in all the mysterious reports – some unreliable, some falsified, some genuine that in actuality have nothing to do with chairs, etc.
        Now let’s consider a group of scientists in Scenario 4 and track their work and logic backwards through the scenarios. They notice that a group of phenomena (some of the mysterious reports) could be explained by positing the existence of a certain kind of (invisible) thing with various properties – certain size/shape, typically found on the floor in a certain orientation, made of wood, etc. This realization – that some of the mysterious reports have commonalities that should be investigated together, takes us into Scenario 3 (in which this logical move begins to be retroactively justified). The scientists then start running “tests” to try to give themselves some confidence that their postulated entities actually exist and are the cause of the reports in question – if you find an invisible object with a certain shape, you’ll be able to sit on it, etc. These tests are very often (perhaps always?) confirmatory, and over time, the group of properties defining “chair” (they’ve now been named) becomes fairly stable. The scientists know that if an object (still invisible) has some of these properties, it tends to have the rest, and it should be classified as a chair. The collection of these properties constitutes a working definition of a chair, and basically constitutes its discovery. We now find ourselves in scenario 2. A freak discovery leads a lucky scientist to a method for making chairs visible. She starts a business, and before you know it, we’re in scenario 1.
        This fictional history is, it seems to me, somewhat analogous to the actual history of the discovery of the atom. Prior to the 1700’s, we were basically in Scenario 4 with respect to atoms. The concept had been batted around for millennia in the form of philosophical atomism, but without (to my knowledge) much if any empirical support. Toward the end of the 18th century, we start to move into Scenario 3 along 3 pathways. Chemists (e.g. Lavoisier, Proust) began to codify numerical regularities of chemical reactions. Dalton is generally credited with noticing that these regularities, especially the so-called law of multiple proportions, could be explained by positing atoms. In parallel, the kinetic theory of gases was developed – proposed by Bernoulli in the mid 1700’s, and then developed and fleshed out through the 19th century by Clausius, Maxwell, and Boltzmann. This theory showed how the atomic hypothesis could help explain the thermodynamics laws of pressure, temperature, and volume. The third relevant line of work was on Brownian motion, the random motion of particles suspended in a fluid. The discovery of the phenomenon is credited to (wait for it…) Robert Brown in the early 1800’s, but it was Einstein who in 1905 provided a solid theoretical foundation for the effect, showing how it could be accounted for statistically by the atomic hypothesis. At this point, we have a working definition of an atom – the collective set of properties it must have to explain the above phenomena – and some powerful and successful tests of this idea – the atomic hypothesis is consistent with and helps reductively explain 3 largely independent bodies of physical phenomena. We are now in Scenario 2.
        The main point of the analogy is the following. In Scenario 2, it seems to me very reasonable to believe in chairs, to assert their existence. Indeed, it might seem irrational not to. Now, these claims could be defended in many ways. It would be a miracle for objects to exhibit the collective properties of chairs so consistently, and yet chairs not exist. Of all the explanations for the consistent collective properties of chairs, the existence of chairs is the best. But the point of common sense scientific realism is not to advocate for the no-miracles argument or inference to the best explanation. It’s to make the same points simply and intuitively. Now, if asserting the existence of chairs in Scenario 2 seems obvious or unproblematic, then by analogy, it should be reasonable to assert (at least provisionally) the existence of atoms in 1905 (or even earlier). Claiming that atoms exist is no more exotic or out of the ordinary than claiming chairs exist, and the fact that we can’t see atoms directly doesn’t change this judgement all that much. This is common sense scientific realism.
        And actually, it’s not true that we can’t see atoms directly. We can. Look closely.