I said previously of nondualism, “I’m not sure I can think of any other major philosophical idea that flowered so much in so many different places, more or less independently. I think that gives us prima facie reason to think the nondualists were on to something important.” Nathan reasonably took me to task for this claim in a comment: “Amod seems to overlook that ideas can be successful without being true.”

I don’t think it’s fair to say I overlooked that point: I said the pervasiveness gave us reason prima facie – at first glance – to say think the nondualists were on to something. That doesn’t mean nondualism is true, and I didn’t say that it was. Second glances might reveal something different. And where I think Nathan is right is in asking us to take those second glances. Is nondualism widespread for a reason other than its being true?

I think the question is particularly important because the rationale given for nondualism does often come down to mystical experience of some sort. Sufis like ibn ‘Arabi, as I understand them, believe that practices like dhikr chanting give one an experience of the unity of being (wahdat al-wujūd). More recently the exciting work of Roland Griffiths and other psychologists has used psilocybin to experimentally induce mystical experiences; the subjects of these experiences report a strong sense of the unity of all things, into which they merge.

The latter point is particularly inviting to a skeptic. If drugs can induce an experience of unity, doesn’t that indicate that that experience is a hallucination, comparable to a fever dream – a perceptual error with nothing to do with reality?

To that I say: not so fast. It could be that the psilocybin makes people see something that isn’t real. But it could also be that it makes them see something that is real! Those who have the experience do typically report a high level of confidence that what they saw was real, and that matters. But the skeptics are right that the experience itself – and for that matter the confidence – is not sufficient to indicate the reality of what was perceived in it.

What is sufficient? To answer that question we need to turn back to good old-fashioned epistemology: our other tools for telling true from false. What do we count as a pramāṇa, a valid means of knowledge? Anyone who asks that question nearly always admits that perception is indeed a means of knowledge: it can lead us to error, yes, but it also often leads us to truth. That snake we see could be a rope – but it could also actually be a snake. When psilocybin or dhikr lead us to perceive the unity of all things, is that perception correct?

Typically when we want to ask whether is a perception is correct, we verify it with another perception. Is that a rope or a snake? Look at it more closely (being careful not to get bitten if it is a snake). Did I smell gas in the kitchen? Check the burners to see if they’re on. But that does not seem an appropriate means of verification in this case. Even if one can seek different means to mystical experience – it is possible, after all, to take psilocybin and practice dhikr – if one of those turned out to be a mere error induced by a change in brain chemistry, there’s a good chance the other one was too.

So what then is a good way to verify whether the world actually is nondual? Here, I think, it matters a great deal that, as I noted in the earlier post, most nondual philosophers actually don’t cite mystical experience as the main justification for nondualism; indeed, as in Śaṅkara’s case, they often don’t cite mystical experience as a justification for nondualism at all. Many of Śaṅkara’s own justifications are scriptural, but that won’t persuade anyone who does not share his faith in the Upaniṣads. Yet Śaṅkara is in debate with Buddhists who do not share that faith, and so he must also make logical arguments why everything must be one. He is far from alone in that. And I think it is the logical case for and against nondualism that can give us the most reliable guide to whether nondualism really is the most accurate way to talk about ultimate reality.

One way logical inquiry explores the possible truth of nondualism is in the very old quest for a first explanation, a quest that goes back at least to the Bṛhadāraṇyaka Upaniṣad (circa 700 BCE, according to Patrick Olivelle). Centuries before Thales would look for an originating principle of all things and discern that it must be water, Gārgī Vācaknavī (one of the few major female characters in early philosophical literature) also observed that “this world is woven back and forth on water”. But Gārgī made this observation only to ask the next question: “on what, then, is water woven back and forth?” The sage Yajñāvalkya replied it was woven on air – to which of course Gārgī asked what the air is woven on. The sequence of recursive questions (“and what is that woven on?”) continues for a while, until Gārgī asks what the worlds of Prajāpati the creator are woven on, and Yajñāvalka names braḥman, that supreme principle that later Vedāntic tradition would identify as the ultimate. Gārgī asks one more time what braḥman is woven on, and Yajñāvalkya tells her “Don’t ask too many questions, Gārgī, or your head will shatter apart!”

That, of course, is a completely unsatisfying answer. But Gārgī’s questioning shows us how, in India and in Greece, inquiry into the nature of things winds up being a search for a first principle. Where will that search end up, if not with a huffy dismissal that the questioner is asking too many questions? It could end up in an infinite regress (turtles all the way down), but when one is asking for ultimate explanations such a regress poses its own problems: as MacIntyre argues, the infinite regress must then itself be explained. For MacIntyre, the series of questions “can terminate only with a being, not itself a member of the series, which makes it the case that this particular series exists.” This gets us to some sort of ultimate as a first principle and first explanation. It does not necessarily get us to nondualism per se – it could be Sirhindī’s “all is from him” – but it gets us somewhere close.

Coming from a different angle, the key test that logic most often applies is coherence. How well does a given idea fit with the other ideas we already take to be true? As always, contradictions are bad (even for Mādhyamikas). But short of actual contradictions there are also what Aristotle would call puzzles (aporiai): places where we perceive apparent contradictions that might not actually be such on a closer look. Getting to truth involves resolving these puzzles, though there are typically so many that we can’t get at all of them.

In my case, one of the driving puzzles is that I have found myself endorsing a position of two truths, in a manner that brings together Wilfrid Sellars and classical Buddhism. But such a position immediately raises the question: what is the relationship between the two? Hegel would have argued that, if we are seeking a most fundamental explanation, then it is that relationship itself that must constitute that explanation. (And so Hegel himself ends up in a certain kind of nondualism, with Spirit as the ultimate.) In China the Tiantai thinker Zhiyi posited a “middle truth” to relate conventional and ultimate, without making the ultimate more fundamental as Hegel does – but it seems to me that this just makes the problem knottier, for now we have to address the relationship between three truths and not only two. There are at least some puzzles that get resolved if one posits a single ultimate and provides reasons why explanation should terminate with that ultimate. Additional puzzles then arise: what is the relationship between that ultimate itself and that which it explains? (I think such a problem may underlie both Plato’s so-called Third Man Argument and Rāmānuja’s critique of Śaṅkara.) I do not by any means think that I have reached a satisfactory resolution to these questions. Yet the logical arguments pointing to an ultimate do give me some reason to think that when the mystics feel certain they have encountered an ultimate reality, we have some reason to believe them. And that the worldwide pervasiveness of nondualism is not just a pervasive error.

Cross-posted on the Indian Philosophy Blog.