Why is the topic of omniscience relevant in Indian philosophy? Because of at least two concurring reasons. On the one hand, for schools like Buddhism and Jainism, it is a question of religious authority. Ascribing omniscience to the founders of the school was a way to ground the validity of their teachings. Slightly similar is the situation of theistic schools ascribing omniscience to God, as a way to ground His ability to organise the world in the best possible way. On the other hand, for other schools the idea of omniscience was initially connected with the result of yogic or other ascetic practices. In this sense, omniscience was conceptually not different from aṇimā `the faculty to become as small as an atom’ and other special powers.

The range of omniscience
A problem (raised by Sudipta Munsi in a comment on this post) connected with the scope of omniscience regards the question of whether an omniscient being also knows all erroneous beliefs. At first sight it might seem that if she does not, she is not completely omniscient and that if she does, she shares also erroneous beliefs, which seems paradoxical. A possible way out consists in claiming that she knows all erroneous beliefs but she attributes them to us. In other words, she knows that I do not know about the place and year of birth of Kumārila, but still correctly knows where and when he was born. Is this solution satisfactorily? Possibly, although this kind of omniscience would lack the first person grasp on how it feels to not know that X or to hold a false belief.

A connected problem regards specifically God’s omniscience: Does God also knows what it is to be in pain? If He does not, He seems to be not omniscient. If He does, He is no longer untouched by sufferance (duḥkha), as claimed in Nyāya and Yoga. In other words, an Īśvara-like God (see below) cannot be said to have experience of duḥkha. His knowledge would nonetheless not be incomplete because duḥkha would be conceived as just a negative entity (the absence of pleasure), which does not need to be separately known. God would be omniscient insofar as He knows all states of affairs, without needing to know also their corresponding absences. By contrast, God as conceived in theistic Vedānta (see below the lines on Viśiṣṭādvaita Vedānta) can even be said to have experience of duḥkha, insofar as He is the inner controller of each conscious being and shares therefore their experience from within.

God’s omniscience
Nyāya authors accept the existence of a God, usually referred to as Īśvara, who can be proved to exist, and develop on this basis a rational theology which accepts His omniscience and omnipotence. They explain that Īśvara `Lord’ needs to be omniscient in order to deploy His functions, which include the re-arrangement of the world after each periodic destruction and the re-assignment of their karman to each living being. Accordingly, God’s omniscience needs to be understood in a robust sense as the knowledge of all present, past and future states of affairs and as completely actualised (against some Buddhist conceptions discussed above). This, however, entails some problem, insofar as the Lord’s knowledge needs to be at any time complete and is in this sense atemporal. But this seems to mean that (a) there is no space for human free will and (b) the Lord knows the world outside of time. He knows, in other words, all states of affairs simultaneously and independent of time. This mirror-like omniscience has been criticised by authors of the Buddhist epistemological school (see Moriyama 2014 and forthcoming).

Śaiva authors, especially of the Pratyabhijñā school, accept both omniscience of yogins and of the Lord/Īśvara. The first one is often referred to in discussions aiming at establishing the omnipresent nature of the Lord as the supreme subject. In fact, how could memory be possible, if there were not a single subjectivity connecting events from a subjective point of view? And how could knowledge be possible, if there were not a fundamental similarity of nature between knower and known things, which does betrays its partaking to the nature of the absolute subject? The Nyāya account of a plurality of subjectivity is rejected insofar as it clashes with cases like the yogins’ ability to access other minds. The yogin, explain Pratyabhijñā authors, knows other minds from within, as the subject of their thoughts, and does not take other minds as an object to be known, since this knowledge would not be a real knowledge of the other mind, which is intrinsically subjective and cannot be reduced to an object. This ability of the yogin depends on the fact that he has recognised his identity with the Lord and can therefore access any mind. The Lord, as the single all-pervading subject, is in fact de facto omniscient and liberation consists in recognising one’s identity with Him (see R. Torella’s studies on yogipratyakṣa in this school).

Vedāntic authors conceive of God as brahman, and therefore as the only absolute reality. In this sense, the brahman is not an additional entity in the world, and the latter only exists because of Him (Dvaita Vedānta), in Him (Viśiṣṭādvaita Vedānta) or does not exist ultimately (Advaita Vedānta). Knowledge is considered in Vedāntic school to be a substance. Advaita Vedāntins resolve the duality which would emerge out of the assumption of brahman and knowledge by stating that brahman consists of cit `consciousness’. This is unintentional, since any content would include duality.

Viśiṣṭādvaita Vedānta authors conceive of God as brahman and at the same time as a personal God. He is therefore the material cause of the world, which is conceived by Viśiṣṭādvaita Vedāntins to exist only as a specification of Him. Like in the case of Advaita Vedānta, knowledge is conceived as a substance. Unlike in Advaita, knowledge is intentional, and has as its content the whole world. The reality of the world is thus guaranteed by its being a specification of the brahman and by its being a content of His knowledge. At the same time, the brahman is conceived of as a personal God, which means that the two above mentioned ways of relating to the world are not mutually exclusive (as it happens to be the case in Spinoza’s pantheism). Rather, knowledge is connected to Him as His characteristic. It is not just one characteristic among many, nor is it connected to the Lord as a quality to its substrate. By contrast, Viśiṣṭādvaita Vedānta authors describe the relation between God and His knowledge as one of indissolubility. The two cannot be experienced the one without the other and, although knowledge is ultimately a substance, it behaves as a characteristic of Him (it is therefore called dharmabhūtajñāna `cognition [behaving] like a characteristic’).

Against omniscience
Basing on the same elements, the authors of the Mīmāṃsā elements altogether deny the possibility of omniscience. They explain that omniscience contradicts our experience, where knowledge always increases but never reaches on outmost limit. Against the argument of repeated exercise, they observe that exercise does not need to be able to reach whatever result. For instance, no matter how much one exercises, one will never be able to jump until the moon. Nor will one’s smell be able to perceive sounds, even after an intense training. Thus, there are intrinsic boundaries to each faculty, including one’s intellect, which cannot directly grasp things, without the mediation of perception, inference and the other instruments of knowledge.
Moreover, no one could judge the omniscience of someone else. Thus, claim the Mīmāṃsā authors, the accounts about the Buddha’s omniscience cannot be trustworthy, since no one but an omniscient can vouch for someone else’s omniscience.

Why do Mīmāṃsakas insist so much on the impossibility of omniscience? From an internal and argumentative perspective, because of their commitment to common experience, which should not be contradicted without a valid reason. From an external and socio-philosophical perspective, because their defence of the Veda depends on its uniqueness as instrument of knowledge for knowing dharma `duty’. It is clear that no other human instrument of knowledge could compete with the Veda, since all human instruments of knowledge can only grasp what there is and not what ought to be. However, if there were an omniscient human or divine being, then they could reasonably compete with the Veda and possibly even falsify it.

The Buddhist arguments against omniscience (see Moriyama 2014 and Moriyama forthcoming) are different, insofar as they object only against the Lord’s omniscience, but accept the Buddha’s one. The difference lies in the fact that the Buddha became omniscient, whereas the Lord is allegedly permanently omniscient. Hence, only in the case of the Lord’s omniscience one encounter paradoxes such as the ones seen above and regarding the incompatibility of temporality and omniscience.