Published in the Philosophical Review, 2020

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I once had an amazing dream.

I was walking on the grass in a sun-bathed field, while up in the sky I saw two excessively big birds, stretching their huge colourful wings but not moving at all. They were suspended in the air, stationary in the sky, as if frozen. I wondered how they could be high in the sky without any movement, but then I somehow realised that the birds were in fact moving their wings, however their time scale was so different to mine, that one second of their flight was like one long day for me, and that’s why I did not notice the utterly slow movement of their wings, thinking they were stationary in the air.

The dream was so vivid that the image of the suspended birds accompanied me long after I woke up. Checking my email, I found messages from a philosophical blog running a thread of comments about the subject of ‘Existence’.  A participant in the discussion asked a question about the existence of “non-existing objects”: ‘Does the flying horse unicorn, Pegasus – does it exist?’.  The discussion was filled with comments, rich in references and names of prominent philosophers (who examined the subject of the existence of imaginary objects – in detail). I thought that rather than questioning the details of what I dreamt  (the ‘non-existent’ stationary birds) – a meaningful question would be on a more general subject: about this puzzling phenomenon we experience every night: the question of …

Do dreams exist?

The answer, perhaps, is ‘yes’ and ‘no’.   Dreams do exist – as we simply experience them, but – bizarre as they are – they do not exist in the domain of physical reality. The flow of events in a dream is not conditioned by the laws of spatiotemporal reality, so their contents cannot materialise in a physical existence.

Linguistically at least, here we have a situation that, at the same time, the contents of dreams neither exist (in the physical reality) nor they do not exist at all (as we vividly see them).  However, to say that something exists and does-not-exist – in the same time – is not a welcome statement in the way we think about consistency and contradiction.

Could this contradiction be a key for re-examining the usage of the word ‘existence’ - indiscriminately employed when referring to objects in the physical reality - as well as to objects in the mental domain? Instead of starting our investigation from what well-known philosophers have to say about the subject, it seems worthwhile to investigate the common wisdom of ordinary people, who – when informed that something exists – would spontaneously ask: where?

This intuitive association of ‘existence’ with the spatiotemporal reality is extremely important for our drive for security and survival.  Existence for our ancestors was not a subject of abstract speculation; it rather meant life or death.  If danger exists, we must know where, and if something of good fortune exists, we too want to know where.

Existence of things or beings in the physical reality must be associated with location (or a probability for location), and this association constitutes an important distinction for the case of dreams.  What we see in a dream is played out in a void unconditioned by the laws of the natural world. The inwardly-experienced void, full of imagery, we observe in dreams is inhabited by objects and events, whose existence is ‘not physical’. The nature of mental imagery is informational, not material

Mental objects are not composed of atoms and they do not occupy a space. In daily language, we strongly associate the existence of an event (or a happening) as ‘taking place’ in the physical reality.  Although this distinction – and also other properties – imply that ‘mental existence’ is distinct from a ‘physical existence’ – yet the same designation of the word ‘existence’ gets used for objects in both domains, leading to philosophical problems.

Physical existence

Science does not have a problem with the concept of ‘existence’.  There is an interesting admission that ‘existence’ is a problem – but only for philosophy - as we re informed at the conclusion of a comprehensive article about Existence, Stanford University Encyclopedia of Philosophy:

“Existence remains, then, itself a serious problem in philosophy of language, metaphysics, and logic and one connected to some of the deepest and most important problems in those areas”.(1)

So, to avoid this ‘serious problem’ in philosophy - why not start the philosophical investigation based on how physics understands ‘existence of objects or phenomena’? It is safe to trust physics on the subject, as its achievement in detecting the existence of phenomena and particles in the real world is just staggering. For example, it is possible to detect the existence of so called Z-particles (2), which have a lifespan of less than a yocto-second, which is one part of a millionth of a billionth of a billionth of a second (3). Another example is employing the technique of infrared interferometry, which makes it possible to distinguish the existence of an object of the width of human hair from a distance of 10 km (4).  

Physics can verify the existence of objects through tools and instruments, which in turn report their findings to the senses and the mind. Sense datum is the informational interface between the mind and the external world. This is how we know about things we cannot directly see or hear through our sense organs.

The inhabitants of the spatiotemporal reality are phenomena and entities that are detectable by the senses (and their extensions of tools and instruments). Our sense organs operate within the spatiotemporal reality we live in, hence science confirms that physical existence is necessarily associated with the spatiotemporal reality. The underlying criterion of existence implicit in the physical sciences is that any physical entity (or its trace) – existing in the spatiotemporal reality – is that which is detectable by the senses and their extensions of tools and instruments. Such a scientific approach to the concept of existence leaves no room for ambiguity or problem.

Mental experience

The mental domain of the mind includes objects and events that are free from the strict boundaries of spatiotemporal laws of nature, but their informational essence is retained in our memory.  All imaginary constructs, feelings, emotions, ideas, concepts, etc, are inwardly experienced within the mind rather than externally detected by the sense organs.

Although distinct, the mental and physical are inseparable. The field of mind is firmly interconnected with the physical field of existence. Take for example the particular elements of the shape in a mental image - we find that all are ‘borrowed’ from the physical realm. The familiar example of the Pegasus clearly shows that all particular components of this imaginary entity are borrowed from physical reality: the wings of birds and body of horse.

The mental field cannot exist on its own, separate from the physical reality, because it is dependent on what exists in the physical field.  At the same time, objects and beings in the physical field are influenced by emotions, desires, and imagination – which are mental in nature.  This inseparability of both fields describes their nonduality.  Nonduality is a perspective that acknowledges the distinction of two phenomena, but binds them in an integral construct in which both are inseparable.

Neither existence nor nonexistence

While the word ‘existence’ creates no problem when used for contents of the physical domain, using it for the contents of the mental domain creates a serious problem. The physical field has a monopoly on the word ‘existence’ – being well defined by its verifiability in the spatiotemporal reality.  Borrowing from the spatiotemporal reality the word ‘existence’ to describe what does not belong to the spatiotemporal reality – this creates a linguistic problem (starting from speaking about the ‘existence’ of ‘non-existing’ objects).

Stanford Encyclopedia of Philosophy concludes that the problem of ‘Existence’ pertains also to the field of logic.  According to logic, a proposition (A) either exists or it does not exist (¬ A).  This is a two-branched outcome (dilemma).  Another perspective, however – suggested by Eastern philosophy – adds to the dilemma of (A) and (¬ A), the combination of the two elements of the dilemma together – conjunctively and disjunctively. This addition results in what is termed as Tetralemma.  Tetralemma, or The Fourfold Possibilities (5) describes all possibilities of existence of a proposition (A):

“Tetralemma consists of any four alternative propositions such as for example, ‘exist’, ‘does not exist’, ‘both exit’ and ‘does not’ - and finally ‘neither exists nor does not exit’.  It is observed that the existence of all things is summoned up and represented by these four propositions, and that dialectically speaking there is no other possibility”. (6)

In general, for any statement or claim (A) there are four possibilities:

Affirmation:     A is true

Negation:     ¬ A is true

Both above:     A ˄ ¬ A true

Neither above:   ¬ (A ˅ ¬ A) true

This perspective, the Tetralemma, fits a certain category of phenomena, which cannot be described by the twofold logic of either/or.  A photon of light can be described as a particle or as a wave, or as both particle and wave, as well as being neither a particle nor a wave.  Another example is that of dreams: they exist (affirmation), but do not exist (negation) in the physical reality. This means that dreams (both) exist, while their contents do not exist. And in general terms, a dream can be defined as belonging to the category of (neither): neither – existence, nor nonexistence.

Similar to the situation with dreams – what we experience of thoughts and emotions in our mind is non-physical in nature. Mathematical concepts, stories, feelings, etc… emerge in the vibrant void of mind. They do not exist (in the same equal sense of existence) as physical objects in space do, yet we cannot say that what appears in the vibrant void of the mind – does not exist.

A 13-century philosopher, Nichiren observed that ‘existence’ is reserved for that which is verifiable by the senses, such as colour or shape, however the vibrant images of the mind do not conform to such spatiotemporal qualities:

*When we look into our own mind at any moment, we perceive neither color nor form to verify that it exists. Yet we still cannot say it does not exist, for many differing thoughts continually occur. The mind cannot be considered either to exist or not to exist. Life is indeed an elusive reality that transcends both the words and concepts of existence and nonexistence. It is neither existence nor nonexistence, yet exhibits the qualities of both. (*7)

A possible avenue to address the serious problem of ‘existence’, can be through exploring the concept of the vibrant void (also called the field of Emptiness of physical nature).  The Void, or Emptiness, is inhabited by reflections from the physical aspect of reality, yet without abiding by the physical laws. This is why mental objects are inwardly-viewed or experienced rather than externally-locatable (where the word ‘existence’ has validity).

It is also important that we shift our strict approach of Either/Or to a possibility of Neither/Nor.  Generally speaking, our attitude in life, based on giving explanations or judgements with a sharp sword of either this is so, or it is not so) – implies that we know everything.

But we do not know everything.

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