Maṇḍana’s theory of commands centers around his attempt to reduce them to statements of instrumentality. Commanding to X to do Y would amount to say that Y is the instrument to realise a goal of X. Maṇḍana establishes (in his eyes) this point in the first part of the siddhānta within one of his masterpieces, the Vidhiviveka ‘Discrimination about Commands’. This consists in some verses and a very extended autocommentary thereon. The first part of the Vidhiviveka covers objectors, the second one (the siddhānta) opens with six verses and commentary explaining this view.

However, Maṇḍana then has to harmonize this point with the pre-existing Mīmāṃsā account of duties distinguishing between three sets of sacrifices, namely:

1. —nitya karman ‘fixed sacrifice’, to be performed regularly (typically each day), no matter what, but where a performance yathāśakti ‘as much as one can’ is acceptable.
2. —naimittika karman ‘occasional sacrifice’, to be performed whenever the occasion arises (e.g., an eclypse or the birth of a son). As in the above case, yathāśakti performance is acceptable.
3. -kāmya karman ‘elective sacrifice’, to be performed only if one wants their results and which needs to be performed exactly as prescribed (yathāvidhi or yathānyāya), no relaxing of the norms allowed.

Once a sacrifice has been undertaken, even if it is kāmya, its completion becomes compulsory and the way of such completion remains yathāvidhi in the case of kāmya sacrifices.
How can this difference be kept if all commands are nothing but statements about instrumentality? Would not a statement about instrumentality correspond only to the kāmya category?

Maṇḍana dedicates to this problem the next verses and commentary of his Vidhiviveka, where he examines several possibilities. The main constraints, are, again, keeping the distinction between nitya/naimittika sacrifices on the one hand and kāmya sacrifices on the other hand, as well as the distinction between yathāśakti and yathāvidhi modes of performance. He therefore explores multiple possible understanding of śakti ‘ability’, phala ‘result’ and adhikāra ‘eligibility, especially in conversation with Prābhākara Mīmāṃsā interlocutors insisting on how all sacrifices are compulsory and how the mentions of result found in conjunction with kāmya rituals is only a way to identify the adhikārin ‘eligible person’ for their performance. For instance, which kind of result could make it possible for a command about a nitya karman to lead one to perform the sacrifice every single day? Are there really results that are always desired? And even if such a result could be found, why would one need to keep a distinction in the yathāśakti and yathānyāya performance? If all sacrifices are instruments to realise a certain result, why would some of them need an accurate performance and other not so? The situation is further complicated by the presence of elective sacrifices prescribed to people ‘who desire heaven’ (svargakāma). In which sense are they different from nitya sacrifices, that also lead to heaven?

Unfortunately, the Vidhiviveka is characterised by a terse style, to say the least. Maṇḍana was probably so much into the topic that at times he seems to take important intermediate passages for granted and just leaves the reader wonder. Fortunately, a more generous commentator, Vācaspati, solves most of the doubt and adds further interesting discussions in his Nyāyakaṇikā.
Last, Sanskritists and philosophers of duty have a duty of gratitude to Elliot Stern, who created the first critical edition of the text, including also its previously unpublished commentaries.

Curious to know more? We will discuss chapters 12–14 of the Vidhiviveka in this workshop: https://philosophy.utoronto.ca/event/workshop-maṇḍana-on-ritual-duties/