I hope that I can start a series on “keywords” here—those seemingly-simple terms which, although they don’t really belong to a technical philosophical vocabulary, do a lot of heavy lifting in a wide range of philosophical discourses. One could think of Williams; I had something more pedestrian or propaedeutic in mind, which would set out the philosophical contexts in which a word is used and some of the issues surrounding its interpretation. Something like the explanation of the differences between εἶναι and γενέσθαι which anyone interested in Greek philosophy has gotten at some point in their education.
I’ll start with the word bhāvaḥ, and I’ll stick to what I know and hope that others will fill in the rest. It’s usually translated as “existence,” “state of being,” and so on. But it has a fundamental ambiguity that is taken up—seemingly independently—in the traditions of Mīmāṃsā and Alaṅkāraśāstra. It can be derived from the simple root bhū “come into being” and the causative root bhū+ṆiC “cause to come into being, bring into being”; hence it can mean both “coming into existence” and “bringing into existence.”
Verbs are traditionally defined as bhāvapradhānam, “that in which bhāvaḥ has primacy” (for example, in the Nirukta of Yāska). Mīmāṃsakas expanded this idea into their characteristic theory of verbal meaning, in which a verb fundamentally expresses the “bringing into existence” of something (bhāvanā). In formulating this theory, Kumārila relied upon bhāvaḥ as the “hinge” between the complementary meanings of coming-into-being and bringing-into-being. One of the interesting things about this theory is that the ontological vocabulary of bhāvaḥ and bhāvanā comes to form the basis of a theory of language and a theory of interpretation: language is always oriented towards the coming-into-existence of some new thing.
Nāṭyaśāstra and Alaṅkāraśāstra use bhāvaḥ as a term of art for the “emotional states” or “feelings” that serve as causal factors for an aesthetic experience (rasa). The Nāṭyaśāstra suggests two derivations of bhāvaḥ to explain this extended sense: one is that these states simply arise (bhavanti), and the other is that they bring into being the elements of the text (kāvyārthān bhāvayanti). The latter derivation is preferred. As it does in Mīmāṃsā, the more common sense of bhāvaḥ as static state of being is traded for a new sense as a dynamic generative process. The tendency to gloss bhāvaḥ with bhāvayati rather than bhavati reflects the distinctive focus of these discourses on what could be or what should be rather than what is: bhāvaḥ, in other words, is not a current state that can be described (its common and common-sense meaning), but a future state that needs to be engendered by human action (in Mīmāṃsā), or that in respect of which a person is transformed or brought into another state (in the Nāṭyaśāstra, which says that bhāvaḥ pervades a person’s body like fire pervades dry wood).
These are “family resemblances” between the use of bhāvaḥ in Mīmāṃsā and Nāṭyaśāstra/Alaṅkāraśāstra that predate Bhaṭṭa Nāyaka’s synthesis. Bhaṭṭa Nāyaka reintroduced bhāvaḥ into Sanskrit aesthetics and explicitly drew the parallel between “bringing into being” a Vedic injunction by performing a sacrifice and “bringing into being” the content of a literary work by aesthetically experiencing it. These analyses, too, lead us to think of “being” or bhāvaḥ in a certain way: less as an impersonal “happening,” and more as an agentive self-fashioning according to a specified procedure and a given textual template.
Of course, bhāvaḥ also figures in discussions about “existence,” and Halbfass summarizes some of these in On Being and What There Is. But as Halbfass noticed, non-existence (abhāvaḥ) has proven a more interesting and more productive topic to premodern and modern philosophers. In these contexts, the non-causative meaning is taken for granted.