The Principle of Underdetermination

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The Bhedābheda Mind-Body Doctrine

Many people equate the mind to the brain, based on the neuroscientific experiments, in which injecting electrical signals into the brain results in novel experiences. This equivalence is in no small measure the result of the mind-body duality created by Descartes and readily embraced by Christianity as the soul-matter duality. Literally everyone, since that time, has held that the negation of duality entails identity. This article discusses why this belief has no foundation, what the relation between mind and body is, why that relationship differs in the material and spiritual worlds, and how these differences are subsumed under the Bhedābheda doctrine.

According to this doctrine, mind and body are at once different and non-different. In the material world, the mind-body difference is that by observing the body you cannot know a person’s thoughts, judgments, goals, values, emotions, and relationships. However, since thoughts, judgments, goals, values, emotions, and relationships have an effect on the body, therefore, mind and body are also non-different. In the spiritual world, by observing the body, we can know a person’s mind, which means that mind and body are equivalent, and yet, because knowing that mental reality is not thinking, feeling, judging, valuing, intending, or relating in that way, hence mind and body are still different. Thus, mind and body are always different and non-different, although it is never mind-body duality or identity.

Percept-Concept Non-Equivalence

Let’s begin with a simple distinction between percepts and concepts. If you don’t think that percepts and concepts are two separate realities, don’t worry; I’m not insisting that they are right now. I will establish the necessity of this realism as we go along. Right now, we just need an experiential distinction between percepts and concepts to begin discussing the general problem of conscious experience.

Philosophers for the last few centuries have tried to reduce all concepts to percepts, and they have always failed. The most overt of these attempts was Logical Positivism, which set out to prove that all concepts can eventually be reduced to percepts, and whatever cannot be so reduced must be a meaningless concept. They had hoped that ideas like beauty, justice, and morality were such meaningless concepts because we cannot reduce them to percepts. They did not realize that even a simple concept like a chair cannot be reduced to percepts, which is why Logical Positivism failed.

The reason is that chairs can have three, four, or six legs. There can be wooden or steel or plastic chairs. Some chairs can have a backrest and hand rest, while others may not. Some chairs can be fixed while others are revolving. Chairs can be designed for use in a garden, kitchen, offices, or bedrooms. As you can see, you can never reduce the concept of chair to a specific percept, because the concept has many incarnations. That, however, doesn’t mean that the concept-percept association is arbitrary. Fire and water are not chairs. Although you can sit on a tiger or an elephant or a tree, these are not chairs.

Likewise, Willard Quine famously argued that percepts cannot be reduced to concepts because the same data or percept observation can be explained using many different concepts. Even if a concept explains the percepts, it doesn’t mean the concept is true, because it might not explain other percepts. That problem then led to the thesis of falsification, namely, that theories are never verified, only falsified. The alternative theory that explains the new and old data would be a concept that will explain the same percept although in a different way. Hence, percepts are not reducible to concepts, in general.

But if we arrive at the perfect truth, then we can equate all percepts to concepts. For example, it is alright to equate red, round, and sweet to an apple, since from apple you can derive that it is red, round, and sweet. The knowing of apple is summarized knowledge and red, round, and sweet are elaborated knowledge. The summarized is still not identical to the elaborated, but since the elaborated can be derived from summarized, and vice versa, therefore, we can say that they are equivalent. This equivalence exists only if knowledge is perfect. Otherwise, it doesn’t. For most of the remainder of this article, I will assume non-equivalence of percepts and concepts, and return to equivalence toward the end of the article.

Percept-Concept Underdetermination

If you think long and hard about this issue, you will conclude that percepts and concepts underdetermine each other. It doesn’t mean that percepts and concepts are independent. And it doesn’t mean that percepts determine concepts or concepts determine percepts. The situation is very nuanced.

Each percept tells us what the concept cannot be, although it doesn’t tell us what it will be. For example, if you see something red and round, you cannot be sure whether it is an apple or nectarine. But you can be sure that it is not a banana. Similarly, each concept tells us what the percept cannot be, although it doesn’t fix the percept. For example, when talking about a chair, we know for sure that it cannot be fluid, and it should not burn the person sitting on it. But you cannot precisely say what it will be.

This is the meaning of underdetermination—each percept will fix what the concept cannot be, and each concept will fix what the percepts cannot be, but we cannot infer one from the other. Hence, you cannot say that percepts are totally independent of concepts and don’t have any role in deciding the concept, or vice versa. And you cannot say that percepts fully determine the concept or vice versa.

Why Underdetermination is Problematic

The problem is that you can never represent the relationship of underdetermination in logic or mathematics, using an equation of the type X = F(Y). If X is percepts and Y is concepts, then if F exists, Y must determine X. But if F doesn’t exist, then X and Y are totally independent variables. Logic and mathematics force us into the dichotomy that X and Y are either determined or independent.

The relationship of underdetermination is neither one of determination nor one of independence. Hence, it can never be captured in conventional logic or mathematics. That makes it inconceivable.

Mind-body dualism says that mind and body are independent, and mind-body identity says that the body determines the mind. Both these positions are operating under the same idea of logic and mathematics, under which Mind = F(Body), such that mind-body identity insists that F exists, and mind-body dualism insists that F doesn’t. Since logic is conceived in a binary manner, it always follows that F must either exist or not exist, which leads to a mutual exclusion of identity and duality. This binary mutual exclusion implies that if duality is somehow falsified, then identity must be implied.

Thus, mind-body dualism and mind-body identity are simply two opposing poles of the same binary dichotomy in which two things are either identical or independent. Now, if you show any relation between mind and body—e.g., by injecting electrical signals you get some sensations—then it must follow that mind and body are identical because, by mutual exclusion, they are not dualistic.

It is unimaginable how Western thinking has been so caught up in these dichotomies for centuries. But that is the fact, and we can see how it makes elementary ideas like underdetermination inexplicable.

Percept-Emotion Underdetermination

This problem is not limited to percepts and concepts. Rather, it can be extended to a wide variety of categories. For example, emotions underdetermine percepts and vice versa. Let’s consider mental illnesses such as anxiety, depression, and PTSD. Since they have many common symptoms, therefore, the symptoms underdetermine the specific type of mental illness. For instance, all three can cause headaches, so merely by the percepts of headaches, you cannot determine the type of mental illness. This is one of the key reasons why each type of mental illness is often misdiagnosed as others.

Likewise, a given type of mental illness—e.g., depression—doesn’t always create the same percepts. In some people, it can create disorders like overeating. In other cases, one may eat fine, but may not be able to digest the food. Thereby, mental illness doesn’t fully determine the bodily symptoms.

Thereby, emotions underdetermine percepts and percepts underdetermine emotions. If you have a headache, you can rule out nail or beard growth as the cause. But you can’t fix the cause. Likewise, if you have PTSD, you can rule out nail and beard growth as effects, but you can’t fix the effects.

Extension to Other Experienced Categories

We can now generalize this problem of underdetermination to several categories. Within percepts themselves, we can say that observations of the knowledge senses don’t fix the observation of the action senses, but the former restricts the latter, and vice versa. For example, a knife—with some definite shape, size, hardness, etc. obtained by the knowledge senses—does not fix the actions for which it can be employed: A knife can be used to cut vegetables, tighten screws, or attack a person.

Similarly, the actions of cutting vegetables, tightening screws, or attacking a person do not imply the presence of a knife; even a saw can cut vegetables, a screwdriver can tighten screws, and people can be attacked using guns. Again, you can say that a knife cannot be used for certain things, but you cannot say what it will be used for. Then, the things that it is used for can also be done by other things. Therefore, we can assert that the senses of knowledge and action underdetermine each other.

In the same way, we can extend this underdetermination to values, goals, and beliefs. Values restrict possible goals, but they don’t fix the goals. The goals restrict possible values, but they don’t fix the values. Goals and values restrict possible concepts and percepts, but they don’t fix the concepts and percepts. Concepts and percepts restrict possible goals and values, but they don’t fix the goals and values. Your beliefs restrict possible goals and values; however, the beliefs do not fix the goals and values.

Is Neuroscience Really a Science?

Let’s say you insert an electrode into the brain and pass some current. That current is some percept, and the mental experience will be a concept. Since percept doesn’t determine the concept, and yet, there is always a concept, therefore, every electrical current will produce a mental experience, although you cannot predict what it will be. Likewise, since the same current creates different experiences in different people, hence, you cannot explain why the same cause produces different effects in different people. In essence, you can neither make an accurate prediction nor explain the different experiences.

Similarly, electrical current is neither necessary to cause an experience (the experience can be caused in other ways) nor sufficient to cause an experience (because there is a range of experiences that can be created).

Thereby, neuroscience doesn’t satisfy the traditional definition of science, because (a) you don’t get accurate predictions, and (b) the explanations are neither necessary nor sufficient. Neuroscience is still considered a “science” by loosening its definition to the prediction of a range of possibilities and impossibilities using a non-necessary and non-sufficient explanation.

This idea has broad acceptance everywhere because it is true for most everything called “science” today. You will not find academics objecting to the problem, because everyone is in the same situation as a result of the problem of underdetermination. However, since the root cause of the problem is never explicitly stated, therefore, most people are unable to recognize how science is no longer what it was supposed to be at the dawn of Enlightenment. The Enlightenment dream about science has failed, and the new working definition of science is “whatever works to whatever extent”. Of course, the public is never told about the failure of civilizational dreams, until the last hurrah is finally done. Hence, science is continuously marketed as something useful and worthy because at least it is something that is better than nothing. Calling it “not a science” will preempt funding, research, publications, conferences, journals, interviews, prestige, promotion, and tenure.

Modern science is like the British empire toward its end, organizing pompous displays of grandeur for the monarchy to make poor people think that it was still powerful when it was actually collapsing. Sweeping claims of science are like the pretentious displays of long-lost grandeur. They project strength to cover up the fact of a collapsing empire. One such claim is the mind-body identity (1) driven by a dualistic “either independent or determined” mutual exclusion, (b) ignoring the serious problem of underdetermination. That mind-is-the-brain assertion is the pretentious display of grandeur while the problem of underdetermination is the collapsing empire.

The Paradigm of Complementarity

The problem of conscious experience is incredibly complicated because it is defined by numerous categories that underdetermine each other. We can never solve that problem using the models of modern science. We can never reduce the explanation of all these categories to one category because each category is underdetermined by every other category. We can never predict the effects because the effects are underdetermined. Hence, sensation, action, concepts, beliefs, goals, and values, are unique irreducible categories. They are however not mutually independent in the sense that you cannot superimpose arbitrary values, goals, beliefs, concepts, sensations, and actions.

Your actions can tell us what your thoughts, beliefs, goals, and values are not. But we can never identify the precise thought, belief, goal, and value underlying the action. This is why in legal dramas, when the lawyers have circumstantial evidence, they try very hard to establish your mental state—i.e., your beliefs, values, thoughts, and goals—in order to get a conviction because actions alone won’t.

It is far too tempting for me not to note that this is a general paradigm of six perspectives employed all over Vedic philosophy. It appears in the problem of Six Causes—why, how, what, when, where, and who. It appears in describing reality from six perspectives in the Six Systems of Philosophy. And it appears in our experience as the six-fold division into action, sensation, thought, belief, goal, and value. The last four are considered the Antaḥkaraṇa or the “internal instrument” and the first two are called the Sthūla-Sarīra or the “gross body”. They can be loosely equated to the “mind” and “body” of Western nomenclature. And yet, they are neither mutually separate nor are they mutually identical.

We can rather use the term complementarity to describe their nature, which means that each of the six aspects underdetermines the other five; by knowing one of them, we can eliminate many possibilities about the other five, but we cannot fix the other five. However, by defining more and more of the six aspects, we keep narrowing the possibilities of what the remaining aspects can be because even more possibilities have been eliminated by the characterization of successive aspects of experience.

Complementarity in Yoga Practice

Therefore, by changing our sensations and actions, we can change our thoughts, beliefs, goals, and values. Conversely, by changing our thoughts, beliefs, goals, and values—or even one of them—we can change our sensations and actions. Any change made to any of the six aspects will have an effect on the remaining aspects. Thereby, spiritual progress can be made through a moral life, by dedicating ourselves to a superior goal, by the study and analysis of philosophy, by always thinking of God, by meditating on a sound using our knowledge senses, or by using our action senses for serving a great person.

Each of these constitutes a certain type of yoga practice, and they are all useful, because they are complementary, which means if we eliminate some activities from our life, then we restrict the possible thoughts, beliefs, goals, and values. Then, as we fix our life on some activities, then we restrict the possible thoughts, beliefs, goals, and values. Different people can focus on one of these more than others. Accordingly, by doing the thing that we can easily do, we make other things easier.

In the final analysis, we must change all six of them, but we can begin with whatever is convenient. As we progress, we can employ a complementary method to make further progress, because, as we have noted, these six aspects of experience are not separate, and yet, they are not also not identical.

For those more familiar with Vedic philosophy, this is the conclusion of Bhedābheda, which stands for “different and non-different”. Bodily activity is certainly different from the philosophical study. But because philosophical study changes bodily activity, and vice versa, therefore they are non-different.

Pointless Mind-Body Debates

The fact is that tired and tiresome positions of mind-body duality and identity are both false. Empirical evidence shows how both are false—since bodily changes trigger a mental change, therefore, mind and body are not separate; likewise, since bodily change cannot predict the mental change, therefore, they are not identical. The problem is that we don’t have a conceptual framework to understand this empirical evidence. The materialist advances a false agenda about identity although he cannot establish identity. He is successful because people imagine that the only alternative is mind-body dualism. And the dualist advances a separation although he cannot explain the neuroscientific evidence.

In these debates, each side thinks that their position is correct, and whatever doesn’t fit into that position, is either irrelevant, can be explained away, or simply doesn’t exist. This makes the debate endless because you can either keep arguing forever or just shift from one side to another.

Futility is the essence of mind-body debates based on the false dichotomy of identity vs. duality, as both these positions are false. Both sides operate on the same binary logic, and they never employ the principle of underdetermination, which then leads to complementarity. Without these general principles, we can never progress into the understanding of the numerous types of complementarities.

Facet Contradiction Causes Material Change

Through the study of Vedic philosophy, and its confirmation in our ordinary experience, we can say that the soul has six complementary cognitive aspects, called action, sensation, thought, belief, goal, and value. Similarly, there are six emotional and relational aspects. Each aspect is sometimes dominant which means that it is the cause of changes to the remaining aspects. Then sometimes it is subordinate which means that it changes as an effect of the changes to one or more of the other aspects.

In the material world, however, the different aspects of the soul are never consistent, and the soul’s experience evolves to create greater inner harmony. This simply means that we try to align our values, goals, beliefs, and thoughts with each other, and with sensation and action. The entire life is a struggle for this alignment, because sometimes the world forces sensations and actions inconsistent with our values, goals, beliefs, and thoughts, and changes one or more of them, creating an inner conflict. Then to resolve that inner conflict, we act on the world, which produces consequences, which then lead to new contradictions, and the attempt to resolve the inner contradictions.

As we have discussed at the beginning, no aspect of conscious experience is equivalent to the others. This non-equivalence is the evidence of falsity. If red, round, and sweet, are correctly identified as an apple, then there would be equivalence although not identity, because the concept of apple is summarized, and percepts of red, round, and sweet are elaborations of that summary. Truth makes aspects equivalent although not identical. Falsity makes the aspects internally contradictory and causes changes. If this falsity pertains to the self, it can also be called the ignorance of the true nature of the self.

Facet Reconciliation Causes Spiritual Eternity

However, if the true nature of the self is known, then the inner contradiction is resolved, and each person is at peace with themselves. In this situation, each aspect is equivalent (although not identical) to other aspects. Vedic texts identify three further subdivisions within this state of equivalence.

In the first subdivision, the end of inner and outer conflict entails the end of experience; only the self is known, and the self is at peace with itself. Thereby, the person is absorbed in the self. In the second subdivision, the end of inner and outer conflict means a world of perfect cooperation, although with freedom. Freedom means the absence of dependence. Everyone is fully capable, self-reliant, and self-satisfied, and yet, they cooperate as equals rather than compete for domination. This is a perfectly egalitarian society. Finally, in the third subdivision, freedom is replaced by mutual dependence based on loving attraction. Nobody thinks that they are capable, self-reliant, or self-satisfied. Rather, they are so strongly attracted to others that they are helplessly bound and inseparable from each other.

Thus, there are four worlds—(a) the material world of inner and outer conflicts, (b) the self-absorbed world called Brahman devoid of conflict, (c) the self-reliant but cooperative world of freedom called Vaikuṇtha, and (d) the loving and dependent world called Goloka. All these worlds are based on the multifaceted nature of the soul. The difference is that the facets can be (a) contradictory and conflicting, (b) reconciled and silenced, (c) reconciled and cooperative, and (d) reconciled and dependent.

We have to remember that opposites need not always conflict. They conflict if they limit and obstruct each other. They cooperate if they allow each other freedom. And they are the basis of mutual attraction. Three out of these four worlds are free of conflict and contradiction; only the material world is conflictual. Hence, the material world is called duality while the other three are called non-duality.

Mind-Body Equivalence and Non-Equivalence

Contradictions between the aspects make the aspects non-equivalent, but reconciliation between them makes them equivalent. This simply means that in the material world, you cannot know a person’s mind completely by looking at their body; hence, you can say that there is a difference between mind and body. However, in the spiritual world, you know a person’s mind completely by looking at their body, because the body is equivalent (although not identical) to the mind. The mind-body equivalence is that you know what a person is thinking, feeling, valuing, believing, perceiving, and doing by just looking at their body. However, the two are not identical because knowing what they feel is not the same as feeling it.

In the spiritual world, everyone has “bared their soul” and there is no “mental privacy” or ignorance of the other person’s nature. And yet, there is “mental privacy” because knowing others is not being them.

The material world is mind-body complementarity and underdetermination, due to which you see a person’s body but you don’t exactly know who they are. The spiritual world is mind-body equivalence without a mind-body identity, such that you know exactly who they are without becoming them. In neither case do we get mind-body dualism or mind-body identity, hence these are totally false.

The Ubiquity of the Bhedābheda Principle

Both spiritual and material worlds can be studied scientifically if we grasp the principles of equivalence and non-equivalence. However, this science cannot be captured in binary logic because non-equivalence defies identity vs. duality dichotomy, and equivalence still doesn’t imply mind-body identity. Both doctrines are various forms of Bhedābheda. Complementarity with underdetermination is one kind of Bhedābheda, and equivalence without identity is another kind of Bhedābheda. Since both forms of Bhedābheda go beyond binary thinking, therefore, before we can explain this science, we have to understand Bhedābheda via the analysis of experience, philosophy, and the practice of yoga.

Bhedābheda can be known via the analysis of ordinary experience, philosophical reasoning, and mystical practices, and each aspect reinforces the others. Bhedābheda can be explained easily to everyone by exploring the relationship between the facets of experience. It can be arrived at via complex philosophy using concepts like underdetermination, complementarity, dominant-subordinate, cooperation vs. reconciliation, etc. And it can be confirmed by the practice of yoga, as we get more contentment, then voluntary cooperation with the devotees of the Lord, and finally loving dependence on the Lord.

The principle of Bhedābheda through these varied processes tells us about the nature of the soul, how our experience evolves in the material world, and the differences between the various worlds. Finally, if we understand Bhedābheda, then we can easily grasp all problems of modern science and how they are stuck in intractable contradictions and paradoxes, and what the solution to these problems is. This is the power of Bhedābheda that we can succinctly capture everything in a single word—Bhedābheda.

Cite this article as:

Ashish Dalela, "The Principle of Underdetermination," in Shabda Journal, February 16, 2022,