Notes on the tetralemma

The tetralemma is the 'four-cornered logic' employed in Buddhist philosophy which can appear odd to those of us with a western heritage of Aristotelian syllogisms. As I will probably use the tetralemma at some point it is worth posting some notes which I have already written which relate it to some of the things I've been writing about in this weblog.

I think the tetralemma is best understood within the context of the Buddhist doctrine of two truths, the satyadvaya. As previously described, the two truths are typically designated ‘conventional’ and ‘ultimate’. Conventional truth applies to facts about the everyday reality of things, people and events. It is designated conventional in the sense of being the product of human interests and dispositions and does not correspond to anything independently or inherently true. Ultimate truth is deemed inexpressible in the sense that, in the absence of convention, there is no candidate for metaphysics-strength predication, including the ascription of existence/non-existence itself. Significantly, both conventional and ultimate truth has the same consequence – nothing can be said to exist by virtue of its own essence.

The tetralemma is comprised of four propositional formulations expressed positively or negatively.* Where x is any proposition and –x is its negation, a positive tetralemma takes the form of:

x
-x
Both x and -x
Neither x nor -x

I think the positive tetralemma is an expression of the conventional validity of the two truths. The positive import of the two truths is that whilst it is stated that nothing is inherently real, i.e., nothing exists by virtue of its own independent essence, the familiar everyday world is, nonetheless, conventionally real and exists in a way which does not contradict experience. With this acceptance of conventional truth we are not left with an absurd conception of reality in which nothing exists in any sense whatsoever. Thus the contradictory standpoints of (naïve or philosophical) reification and nihilism are repudiated in favour of a ‘middle way’. The four formulations of propositions are traditionally presented in an order in which each view presents a progressively better expression of the middle way perspective whilst each is valid with qualification. Constrained by usual proofs, then, a positive tetralemma therefore permits and commits one to state that, e.g.:

The self is real (conventionally true, i.e., it exists in a dependent reality along with everything else we derive from experience)
The self is not real (ultimately true, i.e., it has no essence)
The self is both real and not real (conventionally real but ultimately unreal)
The self is neither real nor not real (neither ultimately real nor completely nonexistent)

A negative tetralemma takes the form of:

Not x
Not -x
Not (x and -x)
Not (neither x nor -x)

The negative tetralemma is the self-destructing logic of the ultimate truth (the emptiness of emptiness!) which denies the validity of any philosophical assertion of any kind including that of the attribution of existence and non-existence to anything. The import of the negative tetralemma is that it ultimately denies the validity of the doctrine of two truths which is itself designated a conventional truth.

An example would be its treatment of the proposition that "śūnyatā exists in time."

"Śūnyatā exists in time" should not be asserted.
"Śūnyatā does not exist in time" should not be asserted.
"Śūnyatā both does and does not exist in time" should not be asserted.
"Śūnyatā neither does nor does not exist in time" should not be asserted.

The negative tetralemma is purely about what can't be said about śūnyatā and, ultimately, nothing can be said. But even one who is aware of that may make mistakes. I think the fourth lemma is the most common mistake that even the most dedicated mystic may make but is avoided by a thoroughgoing application of the negative tetralemma. In this case the fourth lemma falsely implies the independent existence of time to which śūnyatā can be propositionally related.

*There is some dispute over whether Siddhartha Gautama endorsed the use of the positive tetralemma, but Nāgārjuna is less controversially interpreted as doing so.