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  • Writer's picturechris de ray

'Science, unlike metaphysics, doesn't rely on basic common sense'

In this fourth entry on James Ladyman and Don Ross' Every Thing Must Go, I address the relationship between science and common-sense. One of the key motivations for rejecting metaphysics as it is generally practiced in contemporary philosophy is what Ladyman and Ross perceive to be a crucial methodological difference between said metaphysics and natural science -- namely, that the former relies on unfounded, common-sense intuitions about the world while the latter does not. The authors draw out this point by quoting scientists such as Lewis Wolpert, who contends that

" both the ideas that science generates and the way in which science is carried out are entirely counter-intuitive and against common sense"

...and goes as far as to tentatively suggest that

"if something fits with common sense it almost certainly isn’t science" (1992, quoted on p.12)

They also quote the famed philosopher and cognitive scientist Daniel Dennett, who bemoans that while scientists rightly regard counterintuitive results as highly valuable since they compel to revisit unwarranted assumptions, metaphysicians of mind take violations of common-sense intuition to constitute grounds for refutation (2005, quoted on p. 15).

Metaphysicians do indeed typically rely on common-sense intuitions to evaluate metaphysical theories. For example, if a metaphysical theory implies that there are entities that can be fully present in different locations, metaphysicians will regard it with great suspicion, as it violates our intuitions about what it means to be a single entity. Hence, D. M. Armstrong's view that a property is a concrete entity, fully present in the objects that have them, will need to have some serious explanatory benefits in order to make up for its disregard for intuition.

On the other hand, scientists have often come up with theories that challenge deeply entrenched common-sense beliefs. To give just one example, Young's famous 'double slit experiment' showed that subatomic particles behave radically differently depending on whether or not they are being observed, which contradicts the intuition that the behavior of material (and lifeless) things is more or less unaffected by observation.

There is an important difference between the two intuitions just mentioned. This difference has to do with the source of the intuitiveness of the beliefs in question. The belief that a single entity can't be fully present in two different locations logically follows from our concept of a single entity, which entails that a single entity cannot possess mutually incompatible properties (if location x is distinct from location y, being fully present in location x is clearly incompatible with being fully present in location y). Hence it seems that the intuitiveness of this belief is due to its truth being a logical consequence of our concepts. In contrast, the belief that material, lifeless things don't radically change their behavior when we stop observing them is only intuitive because the material, lifeless objects we encounter in our everyday lives behave more or less the same whether or not we observe them.

Thus it would be illegitimate for critics of traditional metaphysics to say that, because intuitions of the second kind tend to get swept away by increased scientific knowledge, metaphysicians should disregard intuitions of the first kind. Intuitions of the second kind involve the tacit assumption that everyday objects are very similar to remote ones, and this is obviously suspect. Intuitions of the second kind just flow from our concepts, and these seem much safer.

Traditional metaphysicians, however, can't get off the hook so easily, because not all common-sense intuitions they typically rely on are conceptually true. Some are held by metaphysicians because it is thought that, without them, metaphysical inquiry itself would be impossible. For example, arguably, metaphysicians need to presuppose the intuition that our concepts aren't radically misleading, so that they somehow reflect objects and structures 'out there' in the world, and aren't just arbitrary ways of sorting things into conceptual 'boxes'. Otherwise, it would seem that much of metaphysics, while pretending to be about the world, is really just about our language (though a few metaphysicians are perfectly happy with this severely downgraded, linguistic metaphysics).

Can scientists and naturalistically-minded philosophers like Ladyman and Ross therefore accuse traditional metaphysics of naively relying on common-sense intuitive beliefs? Not without accusing themselves in the process -- or so I will argue.

In Scientific realism and basic common sense (2014), philosopher of science Howard Sankey begins by asking whether " the advance of science lead to the overthrow of common sense by scientific theory". He ends with the opposite conclusion that common-sense is the "bedrock" on which science rests. This is in part because scientific methodology, as an absolute minimum, requires scientific theories to conform with observable evidence, which is why scientific theories are rejected or modified when their predictions turn out to be false. But it would be difficult to make sense of this requirement if our senses were utterly misleading, and that the mid-sized physical objects presented to us in perception did not really exist. Why bother to try and make your theory fit with the observations if observation isn't reliable anyway? Thus, Sankey tells us that common-sense gives science its "ontological" basis, since any scientific theory worth its salt must cohere with the ontology of common-sense (i.e. the objects that our common-sense intuitions say exist). Here, Ladyman and Ross could protest that the natures of the basic objects of perception as revealed by the sciences are very different to what we expect them to be based on intuition alone (a table, counterintuitively enough, is mostly empty space). Still, the sciences must presuppose, in line with common-sense, that the objects of perception exist mind-independently -- scientific inquiry couldn't get off the ground if our perceptions were the result of mad scientists stimulating our brains.

In any case, there is another way in which science must rely on common-sense, i.e. by relying on the same kinds of belief-forming methods that we use in our everyday lives. Scientific theories are formed by inference to the best explanation, whereby one thinks up explanations for some piece of evidence, identifies the one that best explains the evidence, and infers that the best explanation is in fact true. We use this mode of inference in ordinary contexts, when faced with surprising states of affairs, like my wife coming home later than usual on a Friday night. The best explanation is that she went to the pub with her colleagues, I hence infer that it is true. This correspondence between the methods of science and common-sense leads Elliot Sober, another philosopher of science, to the claim that

“scientific modes of reasoning (…) are continuous with forms of reasoning that are used in everyday life” (2015, 2).

This, I think, is what Sankey is talking about when he says that common-sense also gives science its "epistemic" base (2014). Note, importantly, that scientists therefore must hold the common-sense intuition that inference to the best explanation is a reliable method.

Ladyman and Ross (ibid, p.7) argue that, whatever principles science must ultimately rest on, these are vindicated by the incredible predictive success of the sciences. In other words, if science does ultimately rest on common-sense intuitions, it has earned the 'right' to do so by virtue of its success. Metaphysics, in contrast, can claim no such success, and thus can claim no such right. But as we have seen in a previous entry, such a response is ineffective, due to being viciously circular.

Ladyman, J. and Ross, D. (2007). Every Thing must go. Oxford: Oxford Univ. Press.

Sankey, H. (2014). Scientific Realism and Basic Common Sense.

Sober, E. (2015). Ockham's razors: A User's Manual. Cambridge University Press.

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