In the course, we spend one week going through Rene Descartes' Discourse on Method - concentrating mainly on parts 1-4 of the work, but looking as well at the discussion of human beings, machines, and animals in part 5. One key theme of Descartes' work is doubt. He employs what is called "methodological" or "hyperbolic" doubt as a tool - that's absolutely distinctive to his approach. And, of course, there are a number of lingering worries that can be raised once Cartesian doubt is introduced.
(I should mention - as a side note - that if you're interested in taking an open-enrollment version of that course, based on the earlier 10-week format (which included more content), I offer it in the ReasonIO Academy at this link - Philosophical World Views and Values).
My students enrolled in the Marist course not only study the text, watch lecture videos, download resources, read through lesson pages, and do some writing assignments. A main dimension of the class - both in terms of their grade (which they definitely care about!) and their learning - develops through their participation in discussion forums. And one of the questions I ask them - to provoke conversation among my students - is "should we doubt everything?"
What Descartes Does Doubt (At First)Cartesian doubt is by its very nature designed to extend very far. In both the Discourse and in his Meditations on First Philosophy, he begins by doubting what he has received through the senses. The examples that he gives indicate that what he means by this is primarily ideas about the world that he gets through sense-perception - that a square tower looks round, or that a stick in water seems bent. It would also by implication include everything that he has read or heard from others - although he does not discuss that as such - since he could have perceived those words wrongly.
He pushes it further to encompass the entire domain of non-perceptual ideas. It could be the case - that is, one could imagine it to be the case - that he is mistaken about geometric proofs, about logical argumentation, about operations within arithmetic. You might call this domain that is brought into methodological doubt that of the very logical structure not only of the world, but of human thought in general.
His famous reflections about the possibilities of confusing the ideas of one's dreams with those of waking reality prove troubling and captivating for many. In fact, in my experience, most people remember this aspect of Descartes' hyperbolic doubt and tend to forget about the others. The notion that we could be deceived right now by being in a dream or a hallucination when we wrongly imagine ourselves to be experiencing things as they are in "the real world" - coupled with the "evil demon" or "evil genius" hypothesis (coming from Meditation 2) - for many that sums up Cartesian doubt.
When you put all three of these together, and follow out their implications, they do extend doubt to nearly everything we take ourselves to have previously learned, all of the reserves of knowledge we might draw upon, even the matters we don't claim to know for certain but just believe plausible. It goes a bit further, actually, since Cartesian "doubt" isn't really just doubt, a wavering or oscillation about what might be true, an uncertainty or weakness of belief. Descartes methodically rejects as false whatever can be brought into doubt, until some grounds for believing it to be true can be discovered or produced.
What Students Think We Should Or Shouldn't DoubtWhen I ask my students what can - or should - be brought into doubt, they generally don't want to go as far as Descartes would take them. They can see that there are many things that we do take for granted that, strictly speaking, are dubitable or controvertable - that can be brought into doubt, or that someone can oppose. Many of those matters, they admit, probably do not deserve the level of credence or confidence that we give to them.
Most of my students concentrate on three domains when they consider Cartesian doubt. They acknowledge that we can be deceived by sense-information - after all, they watch me lecture in videos that portray me as talking to them from their computer or phone screen! They also devote a good bit of thought to the dreaming vs. awake problem, some taking it more seriously than others (I suspect that this has largely to do with one's own experience of dreaming, and the ways in which we depict dreaming in popular culture). Many of the matters they consider fall into that other domain of things that we have not experienced or reasoned through ourselves (or done a combination of both of these), but learned from other sources, generally from other people.
Some of them are willing to entertain that engaging in one period of thoroughgoing, totally honest and consistent doubt about practically everything could be something useful, even needed. I think they picture it as a sort of mental house-cleaning, though - taking the furniture out, scouring everything, maybe getting rid of a few things, buying some replacements, and then taking up residence again. Descartes' own analogy is much more radical - entirely demolishing the structure, laying down new foundations, and then rebuilding (and furnishing) from the ground up.
Quite a few students admit their discomfort or distrust - their doubts, you might say - with adopting a stance of hyperbolic or methodological doubt. Some think that it involves being "too much in ones own head." A Cartesian would "over-analyze everything", or might become depressed. Others point out that "doubting everything" might be useful in some contexts - for example, in the sciences, where we ought to be skeptical about any new claims - but not in others - for example, social work, where one has to deal with clients and act on the basis of the best information we have at the time.
They uniformly reject the possibility of going through life in a constant state of Cartesian doubt. And in one respect, that's good, since Descartes himself definitely does not advocate that course of action. But insofar as - after having studied the Discourse - many of them do think that is his actual position, i.e. that we ought to remain in doubt about practically everything as our general approach to life, they're missing what they could be taking from their brief encounter with the Cartesian method and approach.
What Students Miss About Cartesian DoubtThe entire Cartesian project has several goals, and none of them include remaining in a state of hyperbolic doubt. They are - at least in Descartes' view - advanced by engaging for some period of time in hyperbolic doubt. This thorough-going, universal doubt, is as he says "methodological," and that is an apt term to describe it, for two reasons.
First, it does require a systematic, deliberate set of choices on the part of the person engaging in doubt. It goes against habits we have developed and lived by our entire lives. The person engaging in methodological doubt has to work to maintain it, and this is the very labor involved in the "meditation" Descartes writes about. Second, lexically - and I'm not saying Descartes himself intends this - "method" comes from the classical Greek meth-hodos, and has the sense of a way to proceed along a route. Instead of remaining mired in doubt, methodological doubt has a point, a goal, a purpose.
Throughout part 4 of the Discourse (and most of the Meditations), Descartes is engaged in rebuilding the edifice of knowledge - about the self, about the world, and about God (whatever that is, for Descartes). There are some things that he thinks - after reflection and often after a good bit of rational argument - that we either can't doubt (like "I think, therefore I exist") or that we can't reasonably doubt any longer (like God's existence).
There are, to be sure, many things that we can still doubt to some degree - pretty much anything about the external world, but that doubting no longer means that we have to entirely and automatically reject those things as false. We can use the criterion of clear and distinct conception of ideas (there's a lot more to be said about that), we can proportion the degree of credence to probabilities or likelihoods. We can also - as Descartes outlines in the Meditations - suspend our assent when we dealing with things we don't fully or adequately understand - not allowing our wills to stretch themselves beyond the range of our intellects.
So there remains plenty of scope for doubt after the initial hyperbolic doubt about everything has been put to rest. I suspect that students blur together this subsequent, more moderate doubt about genuinely dubitable matters with the original, earlier, universal Cartesian doubt. And because of that, they raise what are - at least in part - legitimate issues with adopting a policy of doubt as one's general and ongoing philosophy of life. But they miss the point of Cartesian doubt in the process, and that's problematic - which is that it's not just a matter of what we ought to doubt. When we doubt - whether before of after we've worked through and resolved some of those doubts - is even more important a lesson.