What is an action?

Śabara introduces the label bhāvanā to define an action as something which "causes to be" a result, such as rain in the case of a sacrifice performed in order to get rain.

Kumārila further distinguishes between: 1. activities inhering in a conscious agent (arthabhāvanā) and producing a result; 2. activities non producing a result (and possibly inhering in a non-conscious agent as well), such as "to dwell"; 3. activities inhering in words (śabdabhāvanā) and causing the first ones to be.

His commentators debated about the understanding of those categories. Maṇḍana abolished the distinction between 1. and 2. and defined bhāvanā in general as "prayatna", effort. Someśvara repeated this definition, whereas Pārthasārathi Miśra kept to the older definition and preferred to describe a bhāvanā as anyotpādakavyāpāra, an activity producing something else. The Bhāṭṭa authors successive to them all sided with Someśvara or Pārthasārathi. The first ones explained that, though a bhāvanā typically inheres in a conscious agent, it can only be metaphorically said to inhere in an unconscious one.

Prābhākara authors reply by describing alleged actions as just successions of conjunctions and disjunctions with various locations in the space.