Within the Śābarabhāṣya commentary on the Mīmāṃsāsūtra (the foundational text of the Mīmāṃsā school), chapter 1 of book 6 is dedicated to adhikāra. The chapter deals with several cases in a manner which might surprise some readers, because the text does not distinguish a priori between “good” and “bad” cases and rather applies Mīmāṃsā-based reasoning throughout. For instance, an opponent suggests understanding adhikāra as only or primarily grounded on desire and is therefore willing to accept as a consequence that women, śūdras (members of the lower class) and animals have the same adhikāra as male Brahmans to perform Vedic sacrifices. Even more surprising, perhaps, is that the reply by the upholder of the final opinion is not that animals are impure, women are inferior and śūdras are inherently flawed. Rather, they discuss about the other requirements of adhikāra and show why they exclude some of the above categories from the performance of Vedic sacrifices.
To begin with, animals lack the adhikāra to perform sacrifices not because they lack desire (they do have plans), but because 1. they lack the ability to perform them, insofar as they don’t have hands. Moreover, 2. they lack desires regarding the next life, because these desires depend on our being cultivated into desiring something beyond the present life. Thus, wolves etc. can decide to fast, but only because they want health, and not for purposes relative to a next life, because they don’t know about it.
There is then an interesting discussion about poor people and people having some physical disability. It’s easy to see that the latter lack ability and are therefore excluded from having the adhikāra to perform Vedic sacrifices. However, how can one distinguish the case of disabled people who cannot, for instance, look at the clarified butter (because they are blind) and poor people who cannot look at the clarified butter because they lack the substances to buy it? Śabara speaks therefore of a distinction between śakti and sāmarthya. Both terms can be translated as “ability”, but Śabara seems to make them into technical terms in order to distinguish the two cases. Accordingly, poor people temporarily lack the sāmarthya to perform a sacrifice, but this temporary lack of sāmarthya is remediable, because they could acquire the relevant substances later on in their life, whereas they never lost the śakti to perform sacrifice. I will conventionally call the temporary thing being lost (or sāmarthya) ‘capacity’, whereas the thing that poor people don’t loose (i.e., their śakti) ‘ability’. Śabara distinguishes them insofar as the former is bahirbhūta ‘external’, whereas the latter is ātmavṛtti ‘belonging to one’s soul, intrinsic’.
Unfortunately, Kumārila does not keep this opposition and just generically speaks of sāmarthya.
It is also interesting that the debate about disabled people continued through the centuries. Kumārila (a commentator of Śabara and possibly the main author of the Mīmāṃsā school) explains that disabled people lack the sāmarthya (and hence the adhikāra) to perform Vedic sacrifices, but that this does not mean that they cannot reach the same goal, namely happiness in a future life (a.k.a. ‘heaven’). He clarifies that they have a different path open to them, namely that of remaining a chaste student of the Veda and reciting it. This is considered by him to be an easier option and Kumārila needs therefore to explain that it is only open to the ones who lack the ability to perform the more difficult alternative, whereas those who are able to work, get married and perform Vedic sacrifices should certainly do so. Incidentally, the same device will be used by an even later author, Veṅkaṭanātha, to justify the adoption of an easier soteriological path, namely prapatti, instead of bhakti. This path is only open, he points out, to those who are unable to follow the path of bhakti, hence there is no contradiction between the command about a difficult path and an easier one.
Later Mīmāṃsā texts, possibly after Khaṇḍadeva, go back to the duties of disabled people and offer a slightly different solution. They say that disabled people cannot perform elective rituals, because they lack the relevant ability, but they still retain the adhikāra (insofar as they have learnt the Vedas by heart etc.) to perform fixed rituals. In fact, these rituals can be performed ‘as much as one can’, hence a blind person will just skip the command to look at clarified butter etc.