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This week, another foray into the debate over “common sense.” Apologies in advance to those readers who are not interested in this particular topic, or who will find this post’s precision rough going. Common-sense advocate Thill has been by far this blog’s most prolific commenter, and I think advancing the debates in the comments requires taking his views on directly and systematically. Moreover, I think the topic is an important one in its own right. The claims made by Thill, Jabali108, Neocarvaka and Ramachandra1008 in their comments, if they were true, would rule out the vast majority of South Asian philosophical thought (and a great more besides): probably all the philosophy originating in the subcontinent except for the shadowy Cārvāka-Lokāyata school of thought. Only the Cārvākas can be thought to completely exclude “religious” ideas from their worldview; but there is little if anything left to be learned from this school now, since all we have from them is the scantest of fragments. (The only surviving complete text attributed to a Cārvāka is Jayarāśi’s Tattvopaplavasiṃha, which these commenters have already dismissed as not really a Cārvāka text.) If South Asian thought is worth bothering with at all, then we’ll need to defend those conceptions of the world that are in some respects at odds with various elements of “common sense” – which, according to Thill, excludes all “religion.”

As I did last week, I will assume that my readers have read the two posts that preceded this one on the subject; I will not assume that you have read the comments to those posts. In his first comment, Thill very helpfully gives us his definitions of three key terms whose meanings have so far been elusive in this debate:

The word “plausible” also has the meaning “worthy of being accepted as true or reasonable” and this is exactly sense in which I am using that word. Interpreting “plausible” in terms of “apparent truth”, as Amod does, is at odds with this sense.

The word “reliable” means “credible; trustworthy; dependable.” That which is plausible (= worthy of being accepted as true or reasonable) is, therefore, also reliable in this sense.

The word “infallible” means “indubitable; exempt from and incapable of error”. That which is true is also infallible. Truth excludes error and doubt. Hence, knowledge of truth also excludes error and doubt. Therefore, truth and knowledge of truth are infallible.

The distinction made here was surprising to me. As it is described here, the distinction between infallibility (on one hand) and plausibility or reliability (on the other) appears to be a distinction between truth and justification. If something is infallible, that means that it is actually true. If it is merely plausible or reliable, that in turn means that it is worthy of being accepted as true, worthy of our trust, credible, believable – that is, we are justified in believing it. Plausibility and reliability are about justification, not truth as such. And there must be a distinction between the two, for Thill’s entire argument depends on there being a significant difference between infallibility and reliability (or plausibility), and with these terms defined thus, that requires a distinction between justification and truth. If we are only justified in believing those things that are actually true, then only the infallible (that which must be true) is reliable (that which we are justified in believing); but that is exactly what Thill’s argument requires him to deny. For Thill there must exist some claims which are reliable but not infallible; and according to the definitions above, these are claims which are at least potentially false but which we are nevertheless justified in believing. (Unless, of course, the ground of these definitions shifts beneath our feet.) If we are never justified in believing false things, then the distinction between reliability and infallibility – as expressed here – collapses.

So assuming the distinction between truth and justification in this way (thus allowing for the distinction between infallibility and reliability), let us continue to “common sense” – in Thill’s definition of the term, as beliefs which can be learned by human beings without special training (which has also not yet been defined). Thill, as I understand it, wishes to claim that common sense is “worthy of being accepted as true or reasonable” and “credible; trustworthy; dependable” – qua common sense. That is, insofar as something can be learned without specialized training, it is worthy of being accepted as true or reasonable.

Now, let me return to my favourite counterexample. Since we learn without specialized training, from the evidence of our senses, that the sun goes up and down as a thrown baseball does, this fact clearly belongs to common sense as Thill defines it. (And I will reiterate that if common sense merely tells us that the sun appears to go up and down, then it must be superseded by specialized training when it comes to the actual truth, for it tells us only about appearances and not truth. If common sense is to have any of the philosophical weight claimed for it, certainly if it is to be considered reliable, then it must tell us about reality and not merely appearance.) It is for that reason – it has been in response to this claim – that Thill has already accepted or at least implied, repeatedly, that common sense is not infallible. As must be the case, for in this case the conclusions of common sense are simply false.

Now what of reliability and plausibility? If common sense qua common sense is “worthy of being accepted as true or reasonable” and “credible; trustworthy; dependable,” this too must include the false claim that the sun literally rises and falls. Thill introduces the distinction between infallibility on one hand, and reliability or plausibility on the other, in order to claim that every single common-sense claim is, if not infallible, still reliable and plausible. But this set of claims includes the claim that the sun rises and falls. The claim of the sun’s rising and falling, because it is a member of the set of commonsense claims, must therefore be considered “worthy of being accepted as true or reasonable” and “credible; trustworthy; dependable” – even though we have already agreed it to be false. We cannot avoid such absurdities so long as we consider a commonsense claim “worthy of being accepted as true or reasonable” merely on the grounds that it is common sense. (And if you don’t like this example, I reiterate that if common sense is indeed not infallible, there must be cases where it is wrong, and those cases may be substituted here mutatis mutandis.)

Now several of the critiques that the commenters have made to my posts have suggested that they assume common sense is all or nothing: if I say (as I have) that common sense as a category is not reliable, that must imply that every member of the category is unreliable. But, as Ben has rightly and repeatedly noted, this assumption is a pretty basic logical mistake. I have never said that everything which falls in Thill’s category of “common sense” is false, or even that most of it is. I am merely saying this: the bare fact that a claim falls within the category of common sense is insufficient reason to consider the claim worthy of being accepted as true or reasonable. Each claim must be accepted on its own merits, based on the variety of sources of knowledge we have available to us (logic, perception, trustworthy authority). The fact that something is learned without specialized training does not make it worthy of belief, any more than the fact that it is learned with specialized training.

This point (in addition to brevity) is why I entitled the earlier post “lack of training is not reliable” rather than “beliefs achieved without training are not reliable.” Some beliefs obtained without specialized training are indeed reliable, in the sense discussed here; but their reliability does not stem from the absence of specialized training. I reiterate: the fact of a belief’s being learned without specialized training does not make that belief worthy of being accepted as true or reasonable – let alone actually make the belief true.

One further note: So far I have been pushing ahead with objections to the common-sense advocates’ views and their logical flaws. I have not yet addressed a central objection that they have made to my view: that ways of knowing other than common sense (such as science) themselves depend for their reliability on common sense itself. This point should be addressed, especially given some of the claims I have just made in this post, and I intend to do so. (Ben has already made some important points on the topic.) I intend to take it up in a post soon, but this one is already long enough. Let us discuss the matters here in the meantime.