The Nyāya-Vaiśeṣika metaphysics is pluralistic realism. It admits many independent realities which are broadly divided into two classes, namely: being and non-being (bhāva and a-bhāva).
There are six kinds of being or positive realities, namely: dravya or substance, guṇa or quality, karma or action, sāmānya or generality, viśeṣa or particularity and samavāya or inherence.
A-bhāva or non-being stands for all negative facts or all kinds of non-existence. These are the seven padārthas or categories of the Vaiśeṣika.
In the Nyāya we have sixteen padārthas or categories, namely:
pramāṇa, prameya or objects of knowledge, saṁśaya or doubt, prayojana or an end, dṛṣṭānta or an example, siddhānta or a doctrine, avayava or members of the syllogism,
tarka or an hypothetical argument, nirṇaya or ascertainment, vāda or discussion, jalpa or wrangling, vitaṇḍā or cavilling, hetvābhāsa or fallacies of inference, chala or quibbling, jāti or futile objections, and nigraha-sthāna or the points of defeat in debate.
This, however, does not give us the categories of reality, but the topics of philosophical discourse, of which the second includes all objects of knowledge as well as the Vaiśeṣika categories of reality.
Dravya or substance is the substratum of qualities and actions, and the constitutive or material cause of composite things. There are nine kinds of substances, namely:
pṛthivī or earth, jala or water, tejas or fire, vāyu or air, ākāśa or ether, kāla or time, diś or space, ātman or soul, and manas or mind.
The atoms of earth, water, fire and air are eternal, while the compounds made of them are non-eternal. We cannot ordinarily perceive an atom. The existence of atoms is proved by inference.
If we go on separating the parts of a composite thing, we shall pass from larger to smaller and smaller parts till we come to the smallest parts which cannot be further divided.
These minute and indivisible parts of a material object are called paramāṇus or atoms. They are eternal entities and are qualitatively different from one another.
In this the Nyāya-Vaiśeṣikas differ from the Jainas and the Greek atomists who hold that atoms differ in quantity and not in quality.
Ākāśa is one, eternal and all-pervading physical substance which has the quality of sound. It cannot be perceived, but is inferred from the phenomenon of sound which as a quality belongs to no other substance than ākāśa. Space and time are imperceptible substances, each of which is one, eternal and all-pervading.
The soul(ātman) is an eternal and all-pervading substance. The qualities of the soul are: cognition, desire, aversion, volition, pleasure, pain, merit, demerit, etc.
These cannot belong to any physical substance. So there must be an immaterial substance called soul, of which they are the qualities. The soul is different and distinct from the body, the senses, mind, and the stream of consciousness.
Some Nyāya-Vaiśeṣikas hold that the soul is imperceptible and its existence is proved bytestimony of the Scriptures and inference from the phenomena of consciousness like cognition, desire, aversion, etc.
Some other Nyāya-Vaiśeṣikas, however, maintain that the soul is also directly known through internal or mental perception as when one says “I am,” “I am knowing,” “I am happy,” etc.
Although knowledge or consciousness belongs to the soul as an attribute, it is not an essential and inseparable attribute of it. It belongs to the soul only in its embodied condition and is therefore accidental.
With the attainment of liberation through the knowledge of reality, the soul becomes free from its connection with the body and has no experience of pleasure and pain or consciousness of any kind.
Manas or mind is an atomic and imperceptible substance. The mind is the internal sense(antar-indriya) for the perception of the soul and its qualities like pleasure and pain.
Just as external perception requires the external senses, so internal perception requires an internal sense called manas.
The existence of the mind is also known from the fact that we cannot have simultaneous cognitions of many objects, although there may be a simultaneous contact of them with the external senses.
This shows that besides the external senses there is an internal sense which being atomic can be in contact with one external sense at a time. This is the reason why of the many objects roundabout us we perceive only that to which we attend or turn our mind.
Guṇa or quality is defined as that which exists in a substance and has no quality or activity in it. It is a non-constitutive cause of things in so far as it determines their nature and character, but not their existence.
There are twenty-four kinds of quality. These are:
colour (rūpa), taste (rasa), smell (gaṅdha), touch (sparśa) sound (śabda), number (sāṁkhya), magnitude (parimāṇa), distinctness (pṛthaktva), conjunction (saṁyoga), disjunction (vibhāga), remoteness (paratva), nearness (a-paratva), cognition (buddhi), pleasure (sukha), pain (duḥkha), desire (icchā), aversion (dveṣa), effort (prayatna), heaviness (gurutva), fluidity (dravatva), viscidity (sneha), tendency (saṁskāra), merit (dharma), and demerit (a-dharma).
Karma or action is physical movement. Like quality it belongs only to substance, but is different from both. All actions subsist in limited corporeal substances, and not in any all-pervading substance.
There are five kinds of action, namely:
throwing upward (utkṣepaṇa), throwing downward (avakṣepaṇa), contraction (ākuñcana), expansion (prasāraṇa) and locomotion (gamana) which includes all other kinds of actions.
Actions are perceptible or imperceptible according as they belong to perceptible or imperceptible substances.
Sāmānya or generality is the common essence of all the individuals of a class. It corresponds to the “universal” in modern Western philosophy. It is an eternal entity which subsists in an identical form in all the individuals of a class.
Some modern Western realists also hold that a “universal is an eternal timeless entity which may be shared by many particulars.”
They agree further with the Nyāya-Vaiśeṣikas in maintaining that universals do not come under existence (sattā). Universals have being and subsist in substance, quality and action.
There is no universal subsisting in another universal, because there is but one single universal for one class of objects.
In respect of their scope or extent, universals are distinguished into para or the highest and all-pervading, a-para or the lowest and parāpara or the intermediate.
“Being-hood” is the highest universal or the summum genus, “jar-ness” as present in all jars and having no other universal under it is the lowest, and “substantiality” is intermediate- between the highest and the lowest, since it is wider than universals like earth-ness, and narrower than “being-hood.”
Viśeṣa or particularity is the extreme opposite of the universal (sāmānya).
The category of viśeṣa, from which the Vaiśeṣika system derives its name, stands for the ultimate difference or peculiarities of the part-less eternal substances.
The differences of composite things may be explained by the differences of their parts.
But the differences of the partless, eternal substances like space, time, souls, minds and atoms of the same kind cannot be explained unless we admit certain original or underived peculiarities in them, called viśeṣas.
There are innumerable viśeṣas, since the individuals in which they subsist are innumerable. They are imperceptible like atoms.
Samavāya or inherence is a permanent or eternal relation between two entities, of which one is in the other. The whole is in its parts, a quality or an action is in a substance, the universal is in the individuals, and particularity is in some simple eternal substance.
In each case the relation is called samavāya or inherence of the one in the other.
While conjunction (saṁyoga) is a temporary relation between two substances which can exist separately, samavāya is an eternal relation between two entities, one of which cannot exist without the other.
A-bhāva or non-existence stands for all negative facts. The reality of non-existence as distinct from existence cannot be denied. That a thing does not exist in a certain place at some time is as real a fact as that something else exists therein.
There are four kinds of non-existence, namely, prāg-abhāva, pradhvaṁsābhāva, atyantābhāva and anyonyābhāva.
The first means the non-existence of a thing before its production, e.g. the nonexistence of an effect in the cause before it is produced.
The second means the non-existence of a thing on account of its destruction after production, e.g. the non-existence of a jar when it is broken. The third means the absence of a connection between two things for all time, e.g. the nonexistence of colour in air.
Anyonyābhāva means mutual non-existence.
When one thing is different from another thing, they mutually exclude each other and there is the non-existence of either as the other. A cow is different from a horse. This means that either of them does not exist as the other.
The Nyāya-Vaiśeṣika theory of the world is guided by the general spiritual view of Indian philosophy.
In its attempt to explain the origin and destruction of the world it reduces all composite objects to the four kinds of atoms of earth, water, fire and air.
So it is called the atomic theory of the world. But it is not a mechanistic or materialistic theory like the atomism of Western science and philosophy:
It does not ignore the moral and spiritual principles governing the processes of composition and decomposition of atoms.
Further, five of the nine kinds of substances, namely, ākāśa, space, time, mind and soul, are not reduced to material atoms or their relations.
The atomic theory of the Nyāya-Vaiśeṣikas explains only the composite objects of the world, which are non-eternal.
All finite physical objects are created out of the four kinds of atoms in the form of dyads (i.e. compounds of two atoms), triads (i.e. compounds of three dyads each) and other larger compounds arising out of them.
The world is a system of physical things and living beings having bodies with senses and possessing mind, intellect and egoism. All these exist and interact with one another in time, space and ākāśa.
The order of the world is a moral order in which the life and destiny of all individual selves are governed, not only by the physical laws, but also by the moral law of karma.
The creation of the world is explained in the light of the unseen moral deserts (a-dṛṣṭa) of individual selves and serves the end of moral dispensation.
The Nyāya-Vaiśeṣika system combines pluralistic realism with theism and believes in the existence of God as the supreme Self:
God is one, infinite and eternal. He is the omniscient and omnipotent cause of the creation, maintenance and destruction of the world.
He does not create the world out of nothing, but out of eternal atoms, space, time, ether, minds and souls. He is the first efficient cause of the world and not its material cause, i.e. a sort of demiurges or an architect of the ordered universe.
He is not limited by the world in so far as the world is related to Him as His body. He is also the moral governor of the world, the impartial dispenser of the fruits of our actions and the supreme arbiter of our joys and sorrows.
The existence of God is proved by the testimony of the Scriptures and inferences from the principle of causality, the moral law of adṛṣṭa, the authoritativeness of the Scriptures, and so on.
The causal argument, which is the most popular, is this:
All composite objects of the world like earth, water, etc., must have a cause because they are of the nature of effects. That they are effects follows from the fact that they are made up of parts and possess a limited magnitude.
Substances like space, time, atoms, etc., are not the effects of any cause because they are not made up of parts and are either unlimited or infinitesimal. Hence there must be a cause for all composite substances. This cause must be an intelligent agent.
Without the guidance of an intelligent cause the material causes of the composite substances, namely, the atoms, cannot have just that order and co-ordination which enable them to produce these definite effects.
This intelligent cause must have a direct knowledge of the material causes, a desire to attain some end and the power of will to realize the end (jñāna, icchā, prayatna).
No individual soul possesses such knowledge and power. The cause of the world of composite things is, therefore, the supreme Self or God.
The causal argument of the Nyāya- Vaiśeṣikas combines the causal and teleological proofs of God’s existence in Western philosophy.
It shows that the first cause of the world is an intelligent being and that we do not require a separate teleological argument to prove this.
While Western theists believe that God is the cause not only of the order of things in the world but also of the existence of those things with their materials,
the Nyāya-Vaiśeṣikas make God the cause of the order of nature and not of the existence of its ultimate constituents.
Still, their view of God is theistic in so far as it holds that God maintains a continuous relation with the world (being conceived as not only the creator, but also its maintainer and destroyer).
There is also the suggestion that the world of things and beings is related to God as one's body is to one's self.
But these ideas are not properly developed in the direction of a full-fledged theism which makes God the author not only of the order of nature but also of its ultimate constituents, and sees God at the heart of all reality.