Do Dreams Exist?                                                                                                                       by Safwan Zabalawi

Published in The Philosophical Society Annual Review  2020

I saw once 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 than 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 existence of imaginary objects - in details).  I thought that rather questioning the details of what I saw in the dream of the 'non-existent' stationary birds – my question is on a more general subject of  this puzzling phenomenon we experience every night; the question of:

Do dreams really 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 the 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, in 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 would 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 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 a 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, which 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.  At the conclusion of a comprehensive article about Existence, Stanford University Encyclopedia of Philosophy informs that:

“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)

Philosophy, however, has a clear and reliable source of knowledge, in which 'existence' does not constitute any problem.  So, 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 lifespan lasts 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 instrument. 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 aspect is retained.  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 shape elements forming mental images, or other properties and functions found in the physical realm.   The familiar example of the Pegasus clearly show that all elements of this imaginary entity are borrowed from the 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.  In the same time, objects and beings in the physical filed are triggered to action by emotions, desires, and imagination – 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 from 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).  

As Stanford Encyclopedia of Philosophy concludes, the problem of 'Existence' pertains also to the field of logic.  According to logic, a proposition (A) either exists or it does not exist ( .  This is a two-branched outcome (dilemma).  Another perspective, however, suggested by Eastern philosophy, adds to the dilemma of (A) and (the combination of the two elements of the dilemma together - conjunctively and disjunctively. This 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 exits and does not exist', and '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: [not A]    is true

               Both above: [A] and [not A]    true  

               Neither above: not {[A] or [not A]}  true


This perspective fits a 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.  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 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 to 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, which is inhabited by reflections from the physical aspect but without abiding by the physical laws.  This is why mental objects are is 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) - then this implies that we know everything.  

But we do not know everything.



1/ Existence, Stanford Encyclopedia of Philosophy,

2/  Z particle, Encyclopedia Britannica

3/  Metric prefix table, (yocto 10 ^ -24)

4/  Images show planets starting to form

5/  Tetralemma

6/  Nagarjuna, Nondualism and the Nature of Nothing, p.123. T. Lorentz, ISBN 978-0-9877782-0-8

7/  “On Attaining Enlightenment in this Lifetime”, Nichiren