Descartes created the mind-body divide and claimed these to be two different substances—the extended substance (res extensa) and the thinking substance (res cogitans). However, with the progress in science (and attempts to subsume thinking under matter), the distinction between mind and body gets hazier by the day. What is the difference between matter and spirit, if any at all?

Dualism in Western and Vedic Philosophies

Vedic texts describe two kinds of creations—material and spiritual. The material creation is said to be made from duality while the spiritual creation is said to be non-dual. The term “duality” or “dualism,” in this context, needs some clarification because the divide between matter and spirit in Vedic philosophy is different from the divide between mind and body in Western philosophy. In Western philosophy the mind-body divide is equated with spirit-matter divide. In Vedic philosophy, both mind and body can be material or spiritual. The mind itself therefore does not equate to spirit.

By dualism, Vedic texts mean that everything in the material creation is built from distinctions or oppositions. For instance, there is heat only because there is cold, there is sweetness only because there is bitterness, and there is dark only because there is light. Indeed, if you touch an object and call it ‘hot’, it is only because your hand is relatively ‘cold’. The universe of distinct objects would not exist if the distinctions between them did not.

This idea of object distinctness is different from that used in current science, where locations in space and time are a priori distinct and hence the objects at those locations are also a priori distinct. In Sāńkhya philosophy, however, the distinctness of locations and objects is created by dividing an undivided or unmanifest existence through distinctions. The consequence of this shift in thinking is that scientific theories cannot describe single isolated objects; they must always describe collections of objects, the smallest collection comprising only two objects.

Dualism and Mathematical Logic

A direct consequence of dualism is that the universe is never consistent because it comprises opposite types of entities. The universe can however be complete through a revision in the scientific foundations if these foundations are based on distinctions rather than objects. The completeness would follow from the fact that all possible objects in the universe can be constructed from some fundamental distinctions. Pockets of this universe can also be coherent (although not consistent) if similar types are aggregated in different parts of the universe. Dualism therefore entails a shift from consistency and completeness to coherence and completeness.

In a consistent and complete universe, proof entails truth. That is, if you construct a statement using logical means, then the statement is true. But in a complete and coherent universe proof and truth are not identical. For instance, I can think that the sky is purple and this thought can be logically produced in my brain (without violating any laws of nature) although the thought itself is false. The production of the thought is proof and the validity of the thought is truth.

The distinction between truth and proof is rather old, but it was first formally demonstrated in mathematics by Kurt Gödel through his Incompleteness Theorem. Gödel, however, viewed the difference between proof and truth as a problem in mathematics rather than a feature of the world in which we can think ideas that may not necessarily be true. If mathematics is consistent and complete, and the universe is a mathematical system (including our brains), then we could not think false ideas because the existence of a false idea in our brain would create a logical contradiction in the mathematical system. If there are no false ideas in our mind, then there is no need for knowledge and discussion itself. The existence of false ideas, therefore, requires a new way of conceiving mathematics where proof is logical but truth is not logical. Rather, truth depends on confirmation with other facts in the world to create coherence rather than consistency. This in turn has profound implications for epistemology.

Dualism allows us to solve the problem of incompleteness without equating proof with truth. Now, the universe is complete and every statement can be proved or disproved, although false things can exist. The book Gödel’s Mistake discusses this problem and its solution.

Non-Dualistic Logic

Armed with this understanding of dualism, we can attempt to understand non-dualism.

Quite simply, in a non-dual universe, proof and truth are identical. That is, if I think that the sky is purple, the sky would indeed be purple. Falsities cannot exist in that universe, because whatever you think would always be true. There is no need for epistemology or a method of knowledge that eliminates falsities, although there is still need for creativity, choice and ideas.

There will still be different things in a non-dual universe, but their difference would not be defined through a mutual opposition or distinction between them. That in turn implies that being “here” does not entail not being “there”. The experience of “now” is not opposed to the experience of “then”. Space and time lose their material distinctness (as defined by duality). Objects in this space-time are individuals, but their identity is not constructed via oppositions.

In the material universe, the qualities of an individual exist because those qualities are missing from another individual. For bitter and sweet to exist separately, they must be opposed. Even happiness and unhappiness are defined in mutual opposition. We call ourselves happy at some times only because we have experienced unhappiness at other times. Some people are happy only because others are unhappy. This universe is complete (all possible ideas and feelings can be created) but it is not consistent because opposite ideas or feelings must exist simultaneously to even create distinctness. This means that in the material universe, no one can be happy at all times, neither can everyone be happy at any one time.

The Vedas state that there is a universe in which everyone can be happy at all times. This universe is produced by the application of non-dual logic. Unlike the material universe where bitter and sweet are defined at once (or not at all), in the spiritual universe bitter and sweet are independent, individual ideas. Therefore, unlike the material world, where bitter and sweet represent a contradiction, in the spiritual world they represent two separate ideas which are not mutually opposed and hence not contradictory. Thus, you can say that something is sweet, but you cannot say that it is not bitter. One never derives the negative assertion based on the positive proposition.

Non-Dualism and Absolutes

Dualism implies that something is hot only in relation to another thing that is cold. No object is therefore absolutely hot or cold. Any qualitative property designation we apply to objects is given only in relation to some other objects. This, in fact, forms the basis of modern science where object properties are defined in relation to other objects, although, post measurement, scientists would like to believe that these measurements reveal object properties existing prior to measurement. This idea about object ‘realism’ is now known to be false in atomic theory where we can only define objects through collections and never individually. Atomic theory reinforces the idea that objects don’t have properties prior to measurement and the properties revealed during measurement are produced only at the point of measurement.

Dualism therefore entails that no object has an absolute set of properties. Rather, objects are co-created mutually through a distinction (this idea is also called pratītyasamutpāda in Buddhism, sometimes paraphrased in English as dependant co-arising of objects). This in turn means that no object has an individuality of its own; all object identities are mutually defined.

When we step out of dualistic logic, it becomes possible to think of objects that have their own individuality and identity. Individuals can now be said to be self-defined. But this definition also entails that no object is opposed to the other objects even when they have opposite properties. For instance, hot and cold are now different but not mutually opposed. No amount of difference creates a contradiction in the non-dual logical system.

Non-Dualism and Logical Principles

Dualistic logic uses two fundamental logical principles—mutual-exclusion and non-contradiction—which are missing in a non-dual universe. Non-contradiction implies that something cannot be hot and cold at once. Mutual-exclusion implies that something must either be hot or cold. Dualism also implies that hot and cold are either mutually defined or not at all. These three facts about a dualistic universe create a conceptual problem, namely that hot and cold must co-exist but in different objects. Each object is logically consistent but the universe as a whole is logically inconsistent (although the universe can be coherent).

The non-dual universe discards the opposition between hot and cold, and thereby mutual-exclusion and non-contradiction. Individuals have real, absolute and possessed properties and while these properties differ from those in other individuals, there is no contradiction. Both the individual and the system as a whole is logically consistent. Furthermore, since there is no contradiction between hot and cold, by saying that something is hot, you cannot imply that it is not cold. As noted above, you can only make assertions, not negations.

The inability for people to comprehend non-dualistic logic in terms of dualistic principles prompted Sri Chaitanya Mahaprabhu to formulate the philosophical term acintyabhedābheda—which essentially means inconceivable oneness and difference—to describe the nature of spiritual reality. It is inconceivable if we think in terms of dualistic logical principles employing non-contradiction and mutual-exclusion. It can, however, become conceivable in a non-dualistic logic.

The dualistic world is a relative world of mutual distinctions. The non-dual world is an absolute world of identities. Truth and proof are different in the dualistic world, whereas they are identical in the non-dual world. The universe as a whole is always inconsistent in the dualistic world and the universe as a whole is consistent in a non-dual world.

In laymen terms, this means that someone must always be unhappy in the dualistic world at all times, and everyone must be unhappy in the universe at some time. But in the non-dual world, everyone can always be happy.