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Spinoza’s Metaphysics & Its Relevance For Science Today

Zoran Vukadinovic thinks Spinoza could help us with our enquiries.

Baruch Spinoza was a Seventeenth Century Dutch philosopher of Portuguese Jewish descent, and a lens grinder by trade. Though mild-mannered and agreeable, he was excommunicated by his community for his ‘abominable heresies’. His most important book Ethics (1677) is concerned with presenting the implications of God’s nature for human happiness. It might surprise you if I said that this work is quite relevant for our time, and that it may even help us understand some perplexing issues in contemporary science, but this is precisely what I will argue in this article. Specifically, I will try to show that Spinoza’s metaphysics, as well as being a good system through which to understand the behavior of elementary particles as described by quantum mechanics, also allows us to demystify the mind-body problem in cognitive science.

Two Modern Metaphysical Positions

The branch of philosophy known as metaphysics is not easy to define, but we can say that generally it is concerned with the basic categories or ideas that underpin reality. It deals, for instance, with substances, causality, identity and emergence, and it relies on our ability to reason about things that cannot be directly observed or measured. In modern science there is a great emphasis on observation and measurement, which unfortunately tends to obscure the importance of theory in science. The discipline of metaphysics can help us make our worldview more comprehensible by integrating insights from science into our overall understanding of reality, which cannot rely on observation alone.

Baruch Spinoza (1632-1677)

Two influential contemporary metaphysical views are scientific reductionism, which is essentially a materialist position, and mathematical idealism, which holds that the basis of space and time is not subatomic particles, but rather, certain mathematical truths. Both positions derive from long traditions in Western thought, and both have merits. Scientific reductionism derives its force from the successes of modern science, which is itself largely a reductionist enterprise – meaning that it tends to explain the complex world in terms of layers of increasingly basic constituents. Mathematical idealism is inspired in particular by the successes of computer science in generating mathematically-based models of worlds; in fact, so successfully that the idea that our universe is itself a computer simulation produced by an advanced civilization has entered the mainstream in philosophy (see ‘Are You Living In A Computer Simulation?’, Philosophical Quarterly, 53(211), Nick Bostrom, 2003).

However, both positions are ultimately unsatisfactory. For example, it’s not clear that the qualities of our experiences can be entirely reduced to or expressed in terms of physical things. And if the world is composed from mathematical truths, the question then arises, how we can have any knowledge of these truths, given that they are outside space and time? Furthermore, if we suppose that these mathematical objects are mental in nature, we could end up with a circular argument: if, as the reductionists suppose, the mind can be reduced to the activity in the brain; and the activity of the brain can be reduced to interactions between nerve cells; these cellular processes to interactions between molecules; molecules to atoms; atoms to subatomic particles; subatomic particles to space-time points; space-time points to sets of numbers; and finally, sets of numbers to the mathematical laws relating them – which some would argue are essentially mental entities – this then loops us right back to where we started (see Reality: A Very Short Introduction, by Jan Westerhoff, 2011).

Spinoza’s Metaphysics: An Outline

Yet before we abandon the metaphysical enterprise to the skeptical view that what underlies the world we experience is essentially unknowable (or worse, uninteresting), let us consider Spinoza’s thought, which, as you will see, is surprisingly compatible with modern science.

Spinoza held that nature – which he equated with God – is absolutely perfect, determined, infinite, and timeless. This infinite ‘God or Nature’ (Deus sive Natura) is all-encompassing. We are all part of it and there is nothing outside of it. We human beings have access to two attributes of this infinite Being – extension and thought – both of which express its infinite essence, and they correspond with each other, because they are expressions of the same reality. Besides thought and extension there are infinitely many other attributes of the infinite Being, to which we do not have access but which are nonetheless expressions of the same Being, which is, moreover, unconstrained by time.

To appreciate how novel this thinking was, it is worth remembering that during Spinoza’s time the predominant view of the universe in Europe was still the medieval notion inherited from Aristotle and Ptolemy of a finite cosmos. As Joseph Ratner points out in The Philosophy of Spinoza (2014), Spinoza’s vision of the universe not only surpasses this ‘pent in’ medieval universe, but also the predominant contemporary view of the universe as a purely physical system. So let me elaborate a little on Spinoza’s metaphysics and present some examples that illustrate why it may be inspiring to anyone who is perplexed by our relation to the universe.

Parallel Worlds 1
Parallel Worlds © Vadim Dozmorov 2016. Contact him at

Spinoza’s Monism

Spinoza’s Ethics is divided into five parts. The first two concern metaphysics, and discuss God and the mind-body relationship respectively. In Part One, Spinoza equates God with the one infinite and unique substance that underlies all of reality. Please note that what is meant here by the philosophical term ‘substance’ is an integrated whole that cannot be directly experienced by us.

Some of Spinoza’s contemporaries and near contemporaries held that there are several substances. Most famously, René Descartes (1596-1650) argued that there are two substances, mind and matter, which have the distinguishing qualities of thought and extension respectively. He further claimed that each individual person is a somehow-interacting union of these two substances. In contrast, Spinoza held that there is only one substance, because it is infinite and all-encompassing, and that, because it is not only infinite and all-encompassing but also creative, is to be equated with God. In the rest of Ethics, Spinoza unfolds the implications of this view for understanding the relationship between the mind and body, and subsequently for our understanding of emotions, knowledge, and ethics.

One of the aims that Spinoza outlines in the opening pages of Ethics is to provide an explanation for the very existence of things. For example, one might ask whether the cause for the existence of existing things is within them or outside them.

Spinoza begins to answer this question by stating that the definitions of entities usually do not include the specific number of individuals of that type that exist. For example, there is nothing within human nature, or in the definition of ‘human’, that specifies that there must currently be seven billion of us. This suggests that the definition of ‘human’, and so our essence, does not determine how many individual humans there will be. Therefore, our existence as individual entities is determined by an entity greater than ourselves. Spinoza then generalizes this observation to postulate that if there are multiple individuals of a type of thing, then the cause of their existence cannot be within them, and therefore that their essence does not involve existence. In other words, it is generally not part of the definition and essence of things that exist that they necessarily exist. This then invites the question: What is the ultimate cause of all the diversity and complexity that we encounter in nature, if it is not those things themselves? Spinoza’s response is that the ultimate source of all existing things – which contains all the other existing things, and without which they would not exist – must be something whose essence does involve existence. And because the definition of this entity therefore involves necessary existence (because it is of its essence to exist), not only does it necessarily exist, it cannot involve any negation to being. This means that this Being is unconstrained, all-encompassing, infinite and eternal. These are the defining characteristics of the cause of all that exists.

This leads to Spinoza’s definition of substance as “that which is in itself and is conceived through itself” (Ethics Part 1, Definition 3). Put another way, substance is that part or aspect of nature that is self-creating (Spinoza and Spinozism, Stuart Hampshire, 2005). To use Spinoza’s terminology, substance is active nature, or Natura naturans (‘the nurturing nature’, or perhaps, ‘nature naturing’) – which he thus equates with God. Moreover, as its very definition involves necessary existence, we cannot deny that this entity exists. And because it is infinite and all-encompassing, there can only be one substance.

Proposing that there is a self-creating aspect to nature is not foreign to the modern mind familiar with Big Bang theory, and we might even say, with the theory of evolution. However, accepting that there is only one such self-creating process (which by reason of its uniqueness we can call God) is more difficult. Moreover, because this entity is absolutely perfect and unique, the term ‘process’ to describe it is not entirely appropriate, since that term entails something that’s developing. ‘Substance’ is a more appropriate term to describe an entity that is not lacking in anything, and thus whose very nature is unchanging.

The human intellect grasps Spinoza’s substance through its two attributes of extension and thought. That is, we can appreciate substance either by contemplating the infinitely-extended physical universe, or else by considering the infinity of ideas possible within it. Reality is for Spinoza both a system of objects, and a system of ideas or representations. Human beings, for example, are bodies composed of physical parts, but are also representations, which constitute human minds. As I mentioned, for Spinoza substance also includes an infinite number of other, unknowable, attributes in addition to the two we can know. In a way, these attributes are what makes something real, distinct – they are the means through which one finite entity may be distinguished from another. In Spinoza’s terminology, each individual in nature is a mode of the one substance.

For Spinoza, thought and extension are conceptually and causally independent of each other, but at the same time correspond to each other, or are ‘mapped onto’ one another. This correspondence of causally and conceptually distinct attributes is known as parallelism, and will be important when we consider the mind-body relationship.

Please note that for Spinoza mind is not the cause of the physical universe, nor is the physical universe the cause of mind. Rather, Spinoza holds that the force behind the existence of corporeal nature and behind the workings of the mind is the same unique and all-encompassing substance, which has both attributes equally.

Parallel Worlds 2

Substance & Science

So God is an entity that exists necessarily, or by definition. It is the self-creating aspect of nature, and is the cause of everything else that exists. The next question is, why is God/nature, as defined by Spinoza, relevant to us today? The answer is that this idea provides a view of the world that is surprisingly consistent with contemporary science, which still lacks a metaphysics that can accommodate its perplexing discoveries.

The first example of its perplexing discoveries is quantum mechanics. It has become a cliché that no one understands the strange behavior of the elementary particles that quantum mechanics describes. For example, how can an unobserved electron be in an infinite number of places at the same time? Or how can a particle of light – a photon – ‘sample’ all of space to ‘select’ the fastest path between two points in space, as Richard Feynman’s interpretation of quantum mechanics would say? One common theme in quantum mechanics is precisely this ‘unconstrained’ behavior of particles. This is consistent with the notion that there is a boundless or infinite aspect in nature underlying the reality we experience – which is precisely Spinoza’s view of substance.

Another theme in quantum mechanics is that the answer supplied by an experiment often depends on the question the experiment is asking. For example, elementary wave-particles can be seen to behave as either waves or particles depending on how an experiment is set up. Furthermore, it seems that observation is required to give quantum entities a determinate form. These two features of quantum mechanics suggest that there is a very close relationship between intelligence and corporeal nature in the universe, just as Spinoza supposed. To put it in Spinoza’s terms, intelligence and the material quantum events that intelligence observes are inseparable because they are two aspects of the same unique and boundless substance.

The anthropic principle in cosmology refers to the striking observation that the cosmos in which we live appears as if specifically fine-tuned to allow life to exist. A number of very basic facts about the Universe, such as the strengths of certain forces (for example, the nuclear forces inside atomic nuclei), and the masses and charges of certain subatomic particles, are of the precise values required for the development of intelligent observers such as us. As the physicist John A. Wheeler summarized in 1986, it appears that “a life-giving factor lies at the center of the whole machinery and design of the world” (see Wheeler’s foreword in The Anthropic Cosmological Principle by J.D. Barrow and F.J. Tipler, 1986). That description could aptly apply to Spinoza’s conception of Natura naturans, nurturing nature.

In summary, modern science provides support for Spinoza’s monism by indicating that there is an unbounded and creative aspect in nature, and also that intelligence and corporeality are intimately bound and inseparable.

Mind-Body Correspondence

Next, let’s turn to one of the most important logical consequences of Spinoza’s monism, namely, the doctrine of mind-body correspondence.

In the first paragraph of Part 2 of Ethics, dealing with the mind, Spinoza makes clear that his conclusions about the mind emanate from his view of God: “I pass now to an explanation of those things that necessarily had to follow from the essence of God, or, an eternal and infinite entity.” As we have seen, God or substance is the self-creating aspect of nature which, because it necessarily exists, cannot be limited by anything, and is, therefore, infinite.

For Spinoza, a human body has the attribute of extension, and a human mind the attribute of thought, or representation. Moreover, the mind and the body are parallel expressions of the one underlying reality; or we could say that the mind and the body are the same thing (substance) considered under different attributes. In language that Spinoza inherits from Descartes, an idea is a representation of the thing of which it is an idea. This leads Spinoza to his famous conclusion that the human mind is equivalent to the idea of the human body. Spinoza’s parallelism also means that every change in the human body has to be accompanied by a change in the human mind: “Whatever happens in the object of the idea constituting the human mind must be perceived by the human mind… That is, if the object of the idea constituting the human mind is a body, nothing can happen in that body which is not perceived by the mind” (Part 2, Proposition 12).

This doctrine of mind-body correspondence is relevant to contemporary cognitive science, where there is increasing recognition of how intimately cognition and embodiment are related. We might say that Spinoza’s argument, put in modern neurological terms, implies that the total representation that constitutes each individual human mind is equivalent to the total activity of that individual’s nervous system, and each operates or functions in parallel with the other. So Spinoza’s metaphysics shows how mind and the nervous system relate. This approach to the mind-body problem is appealing also because it suggests that the mind is not extrinsic to nature, but is one part of an integrated whole. For Spinoza, the double aspect of things (that is, the parallelism) applies to everything in nature, and therefore, everything in nature has a mind of sorts. Human beings do not occupy a metaphysically special place, except in so far as the human body is the most complex thing in nature, and therefore, its representation, or the human mind, is the most sophisticated mind in all of nature. Or as Spinoza says: “to the extent that some body is more capable than others of doing several things at the same time, or of being acted on (that is, suffer) at the same time, to that extent its mind is more capable than others of perceiving several things at the same time” (Part 2, Proposition 13, Scolium). In other words, the sophistication of the human mind corresponds to the complexity of the human body.


According to the contemporary spin on Spinoza’s theories that I have attempted to articulate here, the infinite self-creating aspect of nature underlies (1) the unconstrained behavior of particles in quantum mechanics; (2) the very existence of a world that supports intelligence; (3) the emergence of life forms through evolution. Moreover, all these phenomena that emerge from the one substance are interrelated: there is no intelligence without embodiment; there is no increasing complexity of embodiment without evolution; there is no evolution without a unique universe that allows life to emerge; and finally, as both quantum mechanics and the anthropic principle teach us, there is no observed material universe without intelligence within it. The existence of the universe and of intelligence within it are ultimately expressions of the one substance. The attributes of thought and of extension cannot be reduced to one or the other, but both point to the same infinite and eternal Being. The same boundless power expressed by the complexity of the human body is also expressed by the powers of the human mind. The same power that is behind the unconstrained behavior of particles in quantum mechanics, and expressed by the sheer vastness of the cosmos, also underlies the continual development of human knowledge. There cannot be anything more life-affirming than this. This is what makes Spinoza most relevant to contemporary thought.

© Dr Zoran Vukadinovic 2016

Zoran is an addiction psychiatrist at the University of Colorado, where he works as a medical director of a substance abuse treatment clinic. He and his wife Marina have two children, Andrey and Mila.


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