Maṇḍana reforms Mīmāṃsā philosophy of action and deontic by saying that one undertakes actions only because one believes them to be the means to a desired output.
A problem Maṇḍana needs to face is the following: If the performance of all duties, including that of sacrifices one needs to perform every day, are dependent on one wanting to achieve a certain goal through that performance, how comes that fixed sacrifices can be performed as much as one can? For, says an opponent “If the fixed sacrifices have a result, it is impossible to follow the “as-much-as-you-can” provision, because there would be no result if the sacrifice were defective.” (Vidhiviveka, commentary on v. 2.8)
Maṇḍana’s reply starts by asking what does defectiveness consist of.
Opponent: “The lack of accomplishing what was the meaning of the Vedic injunction.”
Maṇḍana: “Then, there is no defectiveness (vaiguṇya) even in the case of a sacrifice to be performed as long as one lives and performed only as-much-as-one-can (yathāśakti), because such is the meaning of the Vedic injunction (codanā).”
This is clear and a well-devised answer. But then the discussion becomes more complicated, namely:
[Maṇḍana:] If the yathāśakti were not the meaning of the codanā, then there should be all auxiliaries also in the case of a sacrifice which bears no fruit, otherwise the meaning of the codanā would not be realised.
(acodanārthatve vā śakter aphalavattve ‘pi sarvāṅgopasaṃhāraḥ anyathā codanārthanirvṛttyabhāvāt)
[Opponent:] Then, given that there would be nothing to be realised other than the sacrificial action itself, the auxiliaries would not be required.
(tadā kriyāvyatiriktasādhyābhāvān nāṅgāpekṣā)
That is, the opponent says that there is no problem, because in the case of sacrifices without result, nothing needs to be produced over the main sacrificial action, so auxiliaries don’t come into question at all.
[Maṇḍana:] Then we would end up with the situation that a sacrifice has no auxiliaries at all, since (according to your deontic view of action and commands) a sacrifice is not known to be an instrument (for anything).
(anaṅgatvam eva tarhi prāptaṃ karmaṇaḥ nirjñātopāyatvāt)
[Opponent:] Then let it be that also the action requires the aṅgas, for the sake of accomplishing the purpose of the codanā.
The opponent was cornered into a situation in which he should have admitted that sacrifices in general require no auxiliaries, given that for them sacrifices are not undertaken for the sake of their result. He needed to come out of it. But now he cornered himself again, as Maṇḍana aptly points out:
[Maṇḍana:] There would be the undesired consequence that one would have to perform all aṅgas (in all cases).
Maṇḍana’s conclusion as this point is that the Vedic injunctions about fixed sacrifices mean exactly “perform the main action and its auxiliaries as much as you can“.