In Rig-Veda there is a famous Sloka/hymn, which expresses the skepticism about the origin and nature of the world. It also doubts the capability of god and his involvement in the creation of the world. It says the gods may be later than the world creation. At the same time sloka assumes a ‘He’, above the level of gods. Yet even He is not avoided from the net of confusion of the Vedic seer. The seer openly admits that even this ‘highest one’ may not know the beginning of the world. Anyway the world is created or it exists, according to the hymn. Being loaded with realistic arguments, Rigvedic seer does not doubt the real existence of the world. But in later times, parameters changed considerably. Different thought streams sprang up with different viewpoints.
Philosophic speculations began as an answer to a basic question: Do anything exist in this world? The answer was always ‘Yes’, as nobody denied the existence of the ‘existence denier’s or approver’s existence. The existence of ‘something’ in the world got a wide acclamation. But everyone were not in agreement beyond this starting point! Differences soon sprang up about the nature, number and type of the ‘existent reality’.
A short description about the term ‘Reality’ must be provided here. In philosophical sense, if something exists always, independent of other factors, it is called a ‘Real’. This reality should be independent of everything. It should exist by itself without the support from anything. If something cannot exist by itself, but depends on another, for existence, then the latter will be the ground of the existence of the former and thus the ‘Real’ thing. The Real here means, that which is not dependent of anything for its own existence. But everything, except Real, depends on the Real for their existence. Such a Real (or Realities, in the Nyaya/Vaiseshika sense) must have been present in the world because the phenomenal world that we see around cannot root on void because everything in the phenomenal world depend on each other for their existence. So phenomenal world must have a substratum upon which it rests and functions.
The existence of a Real was not a disputable subject. But regarding the nature of Real, philosophers hold different opinions and they stood divided.
Mind and Matter:-
From the outset of the Philosophy, Indians recognized two irreducible entities, which, they suppose, were in no way can combine together. They are Mind and Matter. In other words, an internal phenomenon (Mind) and external phenomenon (Matter). Though they tried their level best to accommodate or reduce these two entities into a single one, they did not succeed in that attempt. And regarding the attempts which were considered as successful, glitches persisted here and there. A perfect system of philosophic thought did not evolve, initially, which reduced Mind and Matter into a single entity.
Mind in its very basic is formless and internal. Its existence and working is in an abstract level. There are no sensations in Mind, but only reflections. Mental sensations are known as reflections. Mind works even in the absence of external world. Mind is filled with many vāsanas or impressions of past. In the absence of external world, vāsanas can present a ‘world’ (like dream, it is argued).
Mind does not have a form, mass or dimension. Then what is it? What are the specifications of Mind? How can we conceive it? Every answer to these questions tends to be ‘internal’. Nobody can think of Mind as external. External is that which Mind experiments. The definition of ‘externality’ itself is related to Mind. For common man, what is outside his Mind (/him) is the external world.
Thus mind and matter (external world) always stand in contrary positions. To mind, what is outside of it, is always something to grasp. But how is it possible? How a mental thing (mind) can grasp a physical, non-mental thing, which cannot think? Physical things, matter, cannot tell or communicate to mind, about ‘what it is’, ‘what is its qualities and nature, etc. Matter will not help mind, to make mind understand about it. Matter will just stand like a mute object, which is unable to move, speak, etc. So it is the job of mind to ‘go near the matter or object’ and grasp the details present in it (from realistic standpoint). Mind also needs to ‘think’ to understand about the Matter. Altogether this is a problematic and complex process. Differences can be easily crop up here. Some of them are given below.
How mind can move from its original habitat to reach near object and grasp the properties of the object, which is by itself a ‘dead stuff’. Mind depends heavily on its auxiliaries like external organs in this process. Do they function correctly? Suppose mind understood the details of an object, i.e. matter, then how can we verify or conclude that the ‘details of the object’ are really with the object or with the ‘mind’, i.e. with the subject? Matter never informs us ‘what all it possess’. Instead we comprehend the details of matter. It is a one-way comprehension. This unilateral working style of mind cannot yield true nature of matter, some argues. So the qualities that we catch from the matter, do they really belongs to matter? Or do the qualities belong to mind itself, but apprehending as outside, of mind, due to certain internal issues?
Anyway what the mind can know about the matter (object) is in knowledge level. Every object is an idea or knowledge to the mind because matter is outside of body, where mind ‘resides’. As long as the object is outside of the body/mind, whatever the mind can conceive of the object is in idea level, not in physical, objective level. I.e. objectivity of the outside world or physical things is converted into an idea level. Thus ideas represent external world.
When an idea represents an object, the predominant ingredient of that idea will be the qualities or properties of the object. Without knowing the qualities of the object, mind cannot prepare an idea of that object. Qualities of the object are that much important. In fact, qualities are that what defines objects in empirical or experimental level. This undistinguishable relationship between the object and its qualities gave birth to diverse views on the mind-matter relationship.
Only qualities exist, matter is a mind construction:-
Since we can ‘know’ the object only through its qualities, only qualities are real. Qualities only exist. Object is a mind construction using the qualities, which are the only reality. And primarily, we know, for sure, that qualities of the objects are inside us, in our idea, through which we understand those objects (matter). Without the ‘internal qualities’ we cannot know which object is this or that. At the same time we cannot say surely that qualities exist in the objects also because we ‘know’ the object only secondarily. Primarily we know the idea (thought) about the object only and this idea carries the qualities of that particular object.
Here, common people may think that the qualities of the object in our idea are generated by the external objects, outside of our mind. This may be true as the Nyāya argues. But this theory has a weak point. We knew that the qualities of the objects primarily reside in us, and so internal to us. Through these qualities we assume that the same qualities are present in the object (matter). Here object’s presence in the external world is a judgment; not a direct perception. This judgment is derived from the qualities present inside the mind. Sensation is happening internally. Internal sensations are different from the sensations from the experimental world. Former is more valid than the latter because former is directly apprehended by the self. It is a one step process (mind to self) avoiding the external world.
So, the contention that the qualities belong to the external object is a judgment. A judgment derived from the internal quality cognition between the mind and self. Then the question remains. Do the internal quality cognitions have an external substratum? Are the object-qualities in our mind is an effect or result of the qualities of the real external objects? There are only two answers – Yes or No – and both views had upholders in Indian Philosophy.
Idealist factions said that object-qualities inside mind have no external object as cause. Then how these qualities came to deposit in mind? Idealists assert that a vast amount of ‘vāsana’ (or impressions of various kinds and types) is in our mind from time immemorial. These impressions spring up in our mind, in random fashion, to make the impression of an external world. According to the first full-fledged idealists of the world, the Vijnānavāda sect of Buddhism, ‘Ālayavijnāna’ is the repository of all vāsana or impression. Mind is the only ‘Reality’ here and the external world is the creation or projection of mind. External world has no objective independent existence apart from mind.
Matter and its qualities exist independent of mind:-
Realist sects of Indian Philosophy propose that qualities of the object reside in the object, in the outside world, which mind grasps. Qualities of objects are not mental by origin. Mind understands the qualities of object after perceiving the object. Thus external object and its qualities exist independent of the perceiving mind. This view leads to Realism and Dualism. Realists assert that mind and matter exist independently. Even when mind is absent, matter (external world) will remain without alteration. This is contrary to the view of idealists according to which, in the absence of mind, external world also disappears.
Samkhya Prakriti: A common substratum for mind and matter:-
Regarding the dualism of mind and matter, Samkhya viewpoint is interesting. According to them, mind and matter are the two different forms of an eternal, evolving substance called Prakriti. It starts to evolve whenever the equilibrium of three guna breaks up. Samkhya defines three gunas: sattva, rajas and tamas. Everything is composed of these three gunas. In which sattva is very prominent it become mind and in which tamas is, matter.
Thus there are various systems of thought in Indian philosophy that speculate and formulated theories about the mind – matter relationship.
 Who verily knows and who can here declare it, whence it was born and whence comes this creation?; The Gods are later than this world’s production. Who knows then whence it first came into being?;
He, the first origin of this creation, whether he formed it all or did not form it; whose eye controls this world in highest heaven, he verily knows it, or perhaps he knows not. (Rig-Veda: 10.129.6-7)
 Also called Subject and Object respectively.
 In Samkhya Philosophy, Purusha and Prakriti represent this classification.
 “In blindness there arose non-enlightenment of which three aspects are to be noted. These three are not independent. The first aspect is ignorant action….. The second aspect is that which perceives [i. e., the ego or subject]…… The third aspect is the external world. Through perception an unreal external world originates. Independent of that which perceives [i. e., the ego or subject], there is no surrounding world [or the object]” – ‘Awakening of Faith in the Mahayana’, Asvaghosha.
 On the other hand, external sensation is a two step process; object – mind & mind – self.
 The philosophical branch which says Mind, idea or thought is the fundamental reality.
 The doctrine that external world exists independent of perception or mind.
 Realists are of two types: Direct realists or presentationists and indirect realists or representationists). Former says we ‘perceive’ the external objects, while the latter says, we only ‘infer’ the external objects. Buddhist Vaibhāsika sect belongs to direct realists and Sautrāntika sect, representationists.