My daughter is at university reading neuroscience. One of her modules this year is philosophy and she is struggling with this question.

"Do we infer the unperceived existence of what we perceive from the nature of our experience? If so, how? If not, why not?"

Can anyone provide guidance,help or suggest sources etc etc as I have no idea.... and nor does she

Any guidance greatly appreciated

Thank you


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    Seems quite straightforward. You perceive some human footprints in your backyard soil ground, and then infer the unperceived existence of someone being there recently... Feb 10 at 20:19
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    @DoubleKnot I think that inference constitutes a degree of perception, so the visitor is not 'unperceived', although his ninja companion might be. Feb 10 at 21:45
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    @ChrisDegnen I’ve never heard of degree of perception, only degree of belief, can you reference it? Per Berkeley to be is to be perceived, therefore any inference result is a perception for him, so you’re essentially proposing the concept of degree of existence? Why perception can be graded like belief? What’s the fullest 100% perception of a being?… Feb 11 at 0:31
  • @DoubleKnot I think it comes down to a quasi-'aesthetic' reflective judgement as to whether one thinks one's deduction is reliable. E.g. "the principle [for judging the form of a thing] leaves it to aesthetic judgment to ascertain by taste whether the thing (its form) is commensurate with our cognitive powers" (Critique of Judgement, 194). In the CPR it's more black & white: "truth and error, consequently also, illusory appearance as the cause of error, are only to be found in a judgement" B350. Feb 11 at 10:15
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    @ChrisDegnen Perhaps either Berkeley or Kant is beyond the scope of OP's non philosophy major intro class, ninja could be a common language here though... Feb 12 at 20:24

7 Answers 7


What the question is getting at is the fact that when you perceive something, such as a yellow cup of coffee, what you actually experience is the sensation of seeing a yellow cup of coffee. The yellowness is a product of your mind interpreting a signal coming from your eye, which in turn is triggered by certain frequencies of light interacting with cells in your retina. The cup itself isn't yellow- your mind creates the yellow image of it.

Likewise when you touch the cup, you might say it feels warm if it is in a certain range of temperature, and cold if it is in a lower range. Those categories are entirely the invention of your mind. The cup has a temperature- which is a measure of how energetically its microscopic components are jiggling around their mean position- which you never actually perceive directly. Instead you experience a sensation of warm or cold which is correlated with the temperature of the cup.

Then consider another method of perception- smell. We say that coffee has a distinctive smell, but that's a figurative expression. Why we really mean is that our minds create the sensation we know as coffee smell, which is triggered when certain molecules evaporating from the coffee interact chemically with receptors in the nose.

Your mind therefore creates a perception of the yellow cup of coffee, which is really just sensations in your head. The properties you experience, such as warmth, colour and smell are not properties of the cup of coffee per se, but are correlated with properties of the cup of coffee which you don't perceive directly.

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    You also need to know what a cup of coffee is (which you didn't mention). Otherwise you are just looking at a hot, yellow smelly thing with trepidation and bewilderment. Feb 10 at 21:53
  • @ChrisDegnen indeed, +1 Feb 10 at 22:15

The way Kant defines objective existence for the observer, existence arises from the joining of concept with sense data:

while possibility was merely a positing of a thing in relation to the understanding (to its empirical use), actuality is at the same time its connection with perception. B287

What exists in this manner is phenomenon. The true nature of the thing is noumenon, but this is unseen and so does not exist (under Kant's definition of existence).

For example, someone feeling around in the dark for a rope. They have the idea of a rope. Then in the dark they find something rope-like and deduce that the rope exists. But let's say the rope is an elephant's tail. (An elephant which no-one has seen.) If one were to "infer the unperceived existence" of the rope one would be mistaken.

In this example the thing-in-itself (the noumenon) is an elephant's tail. (Unperceived, it has never been seen.) The phenomenon is a rope. To the observer a rope exists, and may continue to exist for the foreseeable. Although the rope did not exist for the observer until it was discovered the observer may retrospectively hold that the rope existed before it was discovered, although clearly he didn't know about the rope beforehand.

Here is a longer account of objective existence from Heidegger's Basic Problems of Phenomenology, page 40.

In the proposition "A exists," "A is extant," an absolute positing is involved. Being qua existence must not be confused with being in the sense of "mere position" (being something). Whereas in the Beweisgrund (p. 77) Kant characterizes existence as absolute position, he says in the Critique: "It is merely the position of a thing, or of certain determinations in themselves. In logical use it is merely the copula of a judgment."19 [as the observer joining concept to sense data: (the copula) - my comment] Existence is not "mere position." When Kant says that it is merely position, this limitation holds with regard to the fact that it is not a real predicate. In this context "merely" means "not relatively." Being is not a real predicate either in the sense of "mere position" or in that of "absolute position." In the passages cited, Kant defines the meaning of being as position only with regard to being qua existence. He is elucidating the concept of absolute position relevantly to the connection of the problem with the proof of God's existence.

The preliminary interpretation of being as "mere position" and of existence as "absolute position" should be kept in mind. In the citation from Baumgarten the expression ponitur, position, also appeared. For the real, too, the mere what of a thing, is posited in the pure representing of the thing as in a certain way in itself. But this positing is merely the positing of the possible, "mere position." In one place Kant says that "as possibility was . . . merely a position of the thing in relation to the understanding, so actuality [existence] is at the same time a combining of it [the idea] with perception [feeling]."20 Actuality, existence, is absolute position; possibility, in contrast, is mere position. "The proposition 'God is omnipotent' contains two concepts, each of which has its object: God and omnipotence; the little word 'is' is not, in addition, a predicate but only posits the predicate relatively to the subject."21 In this positing of "is," of mere position, nothing is asserted about existence. Kant says: "Hence also this being [of the copula] is used quite correctly even in the case of the relations which impossible things have to each other, "22 as when, for example, I say "The circle is square."

  1. Critique of Pure Reason, B626.
  2. Ibid., B287 n.; see also Beweisgrund, p. 79.
  3. Critique of Pure Reason, B626-627.
  4. Beweisgrund, p. 78.

Note, the above is about objective existence. The first-hand, subjective existence of the observer is of a different order, hence "the ontological difference". The translator of the above quote uses 'extantness' to denote objective existence: Vorhanden-sein (being objectively present) in Heidegger's parlance. Objective existence is what the observer believes to exist on the basis of concept plus physical sensation or more tenuous physical evidence (requiring a secondary judgement of reliability) such as from telescopes, particle colliders or physical modelling.

Anything completely unperceived such as tachyons or unicorns are fairly not deemed to exist.

In Kantian terminology the kind of unperceived things one might look out for when turning a busy corner are all real possibilities (which would become all too existent upon contact).

The Kantian meaning of the term "reality" is the one that is appropriate to the literal sense of the word. In one place Kant translates "reality" very fittingly by "thingness," "thing-determinateness." The real is what pertains to the res. When Kant talks about the omnitudo realitatis, the totality of all realities, he means not the whole of all beings actually extant but, just the reverse, the whole of all possible thing-determinations, the whole of all thing-contents or real-contents, essences, possible things. Accordingly, realitas is synonymous with Leibniz' term possibilitas, possibility. Realities are the what-contents of possible things in general without regard to whether or not they are actual, or "real" in our modern sense. The concept of reality is equivalent to the concept of the Platonic idea as that pertaining to a being which is understood when I ask: Ti esti, what is the being? (Basic Problems of Phenomenology, page 34.)

An opposing philosophical system is mind-independent realism where all 'things' are posited as existing regardless of what their concept (what-ness) is according to whomever, and whether or not they have been perceived. It is a rather simplified system and of limited use.

"Do we infer the unperceived existence of what we perceive from the nature of our experience? If so, how? If not, why not?"

We ascribe phenomenal existence to things according to perceptual, sense experience combined with imaginative conceptualisation. The phenomenal existence itself is an inference (e.g. a rope, from the earlier example). Unperceived things are not considered to exist, otherwise we would be swamped with unicorns. Also, in physics the ‘existence’ of theoretical things is only theoretical.

Clearer Conclusion

The perceived [phenomenal] existence is determined by conceptualisation plus sense data (perception), supported by reflective judgement of the reliability of the initial judgement. However, unperceived [noumenal] determination should be forborne since this would be advancing from fair judgement to unfounded assertion. It may have been quite reasonable to ‘infer’ the existence of a rope, but to say it is definitively and only a rope (in itself) would be presumptuous. On the other hand, if you made the rope yourself then you could be certain that is what it is.

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Image from The Blind Men and the Elephant: A Metaphor to Illuminate the Role of Researchers and Reviewers in Social Science


The question in its condensed form and without further context sounds a bit strange. Nevertheless, it makes sense when posed in the following form:

Does an object exist even when we do not perceive it? If so, how? If not, why not?

  • Nobody doubts that the moon exists even when I close my eyes and do not look at it any longer. Why? Because that’s the most simple hypothesis, and we do not know any mechanism which destroys and recreates objects like the moon when closing and reopening the eyes.

    Moreover, otherwise assume two persons looking at the moon, and then one of them closing his/her eyes. It is difficult to argue that the moon no longer exists because one of the two observers does no longer perceive it while the other continues to see it.

  • The situation and explanation is different when - looking at a red traffic light – I have a red-perception. When closing the eyes I do not longer have the red-colour perception.

    The traffic light still exists and continues to radiate the same physical wave wavelengths as before. But the colour perception “red” was the subjective way how we perceive the wavelengths of the traffic light. This red-perception terminates because the mental processes which generated the colour perception do not get any longer the external stimulus as input, and therefore they do not generate any longer the output red-perception.

Lessons learned: We have to distinguish between on one hand objective things, whose existence is independent from subjective perception. And on the other hand, subjective perceptions, e.g., qualia like colour perceptions, which are generated by the conscious observer in his mind.

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    Re. “It is difficult to argue that the moon no longer exists because one of the two observers does no longer perceive it while the other continues to see it.” However, to an isolated tribe in the Amazon TikTok does not exist (in Kantian terms). Post-contact they would agree it does exist and previously did too, but that is retrospective knowledge. In the pre-contact tribe’s world there was no TikTok. Feb 10 at 19:31
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    @ChrisDegnen It is not the question whether an object exists or does not exists in the world, i.e. in the worldview, of a given person. The moon exists independently from any particular worldview, and it existed long before humans started to exist.
    – Jo Wehler
    Feb 10 at 20:02
  • Yes, but that is retrospective knowledge. It is meaningless now to talk about the existence of undiscovered/unperceived things because we do not even have a concept of them, except as undiscovered things. That generalisation is fairly given because things have previously been discovered, but it is otherwise of no use because it lacks specificity. Feb 10 at 20:15
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    Color is a particularly interesting example to investigate. There is a such thing as "750 nm light," and nobody would argue that that ceases to exist when you stop perceiving it, but that is not the same thing as "red light." Colors supervene on spectra (per person), so they cannot be identical. Or in plain English, you can get the same color with two completely different spectra, so spectra and colors are not the same thing. Then you add in people who have nonstandard color perception, and thought experiments like inverted spectrum.
    – Kevin
    Feb 11 at 0:33

Your question does not have a simple answer, it leads into an area of ongoing research and thinking in both philosophy and neuroscience

Humans are wired up with neural nets. Data comes into these neural nets from our sensory systems, and gets binned into categories -- such as edge detection, color and tone grouping, etc. These basic data get summed up into categories like shape projection: square, round, upright, flat edge, facetlike, approaching or withdrawing, etc. Some categories get more attention than others, based on risk/reward criteria. This is how our neural nets work, and it had gotten pretty well understood. A few now dated books on this I can recommend are Crick's "The Astonishing Hypothesis", which does a great job outlining how this is done with vision, and Churchland's The Engine of Reason, reviewed here: https://www.amazon.com/gp/customer-reviews/R5048CH7VMV78/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=0262531429

One of the problems for these neural net thinkers, is that we humans START our processing with neural net "thinking" but at some point, we switch over to reasoning with algorithms. Neural nets operate in bins. But we think in concepts and categories, the sorts of things that can be characterized in logic syllogisms. And the WAY we think, is characterized by how we built Von-Neuman Machines, our basic computer architecture. Working memory, step by step operation, moving outputs to short term, and long term memory, a limited suite of logic operations, etc. The problem for neuroscience, is that NONE of this (other than short term memory) has actually been found in their dissections. Daniel Dennett, one of the materialist rivals to Paul Churchland and his reductivism eliminativism about consciousness, postulates that we do all of the above on a "virtual Von Neuman machine" constructed of "software", "running" on our neural net substrate. There is no neurological data to support this "software" speculation, which leaves both Churchland's and Dennett's thinking unmoored from actual observed evidence.

And excellent book that discusses the differences between neural net processing, and algorithmic reasoning, is Thinking Fast and Slow, by Kahneman. Kahneman does not discuss consciousness, or whether neural processing supports his model. He just reports on lab decision studies that revel that we have two "systems" -- one that "thinks" like a neural net, and is very fast, and another that "thinks" with reasoning, and is slow. Most of our system 2 processing is done consciously, although some of it is unconscious, so Kahneman's model does not sort out why we are conscious, because presumably we could have done system 2 processing entirely unconsciously. He just reports on the behavior.

BOTH the binning, AND the process of projecting from the bins into logic categories, PRESUME that the bins and the categories reflect "real" things out in the world. The direct experiences in our sensors are used in a process called Indirect Realism to postulate reality "out there". So yes we "infer the unperceived existence of what we perceive from the nature of our experience". How this is done, is by acting on the binning and the categories and the reasoning about both.

Note that almost all of what you ask about is unconscious. Our consciousness is basically a veto on what our unconscious processing does. And our consciousness does not get any of the raw data from our sensors, nor most of the binning info, and only some of the initial unconscious categorization. What is passed to our consciousness is basically a virtual model of the world, that is VERY sparsely filled in. In many cases it is just logic categories, with a few qualia thrown in for areas of the world that our unconsciousness wants us to focus on, to try to populate a "Grand Illusion" of a "stage set" of the world. The best summary I have found of how this illusion is constructed is from the neuroscientist David Eagleman, in the book Incognito. Eagleman spells out how our introspection is often deluded about the details of what we are perceiving. This deliberately misleading confusion about perceptions, and the very "constructed" nature of our perceptions, are why perceptions are not a great point to start with in projecting to reality. BUT -- they are all we have available to our consciousness.

Once one gets to perceptions which are mostly already in logic categories, the way to more deliberately and consciously build a world model was articulated by Karl Popper. His two best books on this are Objective Knowledge, and Conjectures and Refutations. Popper holds that we only know anything about our world tentatively. We project to reality using indirect realism, and our data, and our reasoning, could always both be in error. Therefore we should continually challenge our conclusions by doing falsification testing on them, to see if we can break them.

Popper's thinking has basically been adopted by science. Although philosophers OF science have pointed out that there are "falsifying test cases" from how science is actually done, that forced Popper and a few others to refine his model of science. Popper's model is a good first approximation of how to do science, with a better but far more complicated model being that of Imre Lakatos.


So -- the answer to your question leads to an incomplete model in current thinking. How inference to reality works is buried in our unconscious processing, how we convert from bins to ideas is a total mystery, the role of perception in this is basically as inputs to a corrective overseer in the System 2 function, how to do System 2 better is spelled out by Popper and Lakatos, and how consciousness is fed the data and illusions of perception is also a mystery.

If your daughter continues in neuroscience, she can have a career trying to explore the mysteries in this process.

  • Re. “Popper holds that we only know anything about our [objective] world tentatively.” This is the same as my statement “The phenomenal existence [of assumed rope] itself is an inference”. However, you have also included a lot of scientific speculation of how the mind works as seen objectively, whereas I have approached it from the working perspective of the mind. Feb 10 at 20:07
  • @ChrisDegnen -- "phenomena" are themselves constructed and highly derivative, with a lot of intentionality and purposeful direction/deception built into them by our unconsciousness. Phenomenalism, which starts with phenomena as the raw data starting point, is therefore going to end up badly muddled. Kant did not understand the agency of our unconsciousness, and he is therefore not a very useful reference. His endorsement of indirect realism is useful, but that is only a subset of what you referenced.
    – Dcleve
    Feb 10 at 20:16
  • Re. "We project to [actuality] using ... our data, and our reasoning, could always both be in error." That is Kant's 'existence', as you agree: (sense data + conceptualisation). As for psychological and psycho-physiological analysis, awareness of unconscious biases is insightful, but still the determination of objective existence is the observer's, for all its imperfectness. In contrast, the noumenal truth is before determination: indeterminate. I think science is quite in line with Kantian and Heideggerian philosophy. Schrödinger's cat is a nice example of observer perspective left as is. Feb 10 at 21:27

First, let's look at a concrete example of an unperceived existence -- that of the Isaac Newton's universal gravity.

The gravitational force is quite weak -- so weak, we only feel its pull from the only object that is massive enough, our planet. Things fall down, that much we knew -- and for the longest time, that was all we knew, having no reason to suspect that there was anything else going on.

Even after the gravity was discovered by Isaac Newton, a whole century had to pass before someone managed to build an experiment sensitive enough to detect (and measure) the gravitational force exerted by something other than Earth -- a massive led ball.

Now comes the million dollars question: How could Newton discover something completely unperceivable at his time? Well, the short answer, is that he saw it in his mind. Remember that "third eye" thing on people's foreheads? -- that's the metaphor for this capacity that some of us develop, the ability to see the otherwise unperceivable phenomena.

A less short answer is that Newton was busy piecing together, in his mind, a model of the Universe -- the Sun, the planets, and their moons circling each other on elliptical orbits. And then, in a revelation, he imagined something else -- a missing piece, something that could drive this cosmic dance. That missing piece was gravity. And then he realized that the same force would also make an apple fall from the tree -- he realized that this gravity was universal.

In other words, we humans have two kinds of experience. One is that of the real world. The other one is our experience in the virtual world that we build in our imagination. That virtual experience is no less valid as long as our virtual world is an accurate model of the real one.

And it is that virtual reality where we can perceive the unperceivable. There we are the gods, we can go anywhere and experience things that we cannot experience otherwise. Like watching hydrogen atoms fusing together in the center of the Sun, like peering inside the mind of a cat -- or our own mind. There we can uncover treasures that are hidden from us -- and then we would know where to look for those treasures in the real world.


"Do we infer the unperceived existence of what we perceive from the nature of our experience? If so, how? If not, why not?"

Nature of our experience seems to refer to features of our senses (we experience via them). Could we be talking about colors/heat/pleasure/pain/etc.? These then (in)appropriately processed and finally presented to our consciousness? A complex interplay between, sensu latissimo, sensations, mental content, emotional state, and so on, whose final product is, what else, a judgment, a feeling that attends that, and a desire to act in a certain fashion by way of a response and subsequently anticipate consequences. In a nutshell, the xin, 心 (Mandarin for heart-mind-(body)).

That there's unperceived existence, distinct from what we perceive hints at mental pathology (hallucinations), which is simply just another way to bring up (radical) skepticism. How reliable/dependable/credible/trustworthy is our nervous sytem, brain and all. As someone mentioned, Kant expounded on the noumenon-phenomenon gap.
I was always of the view that there's no test for existence i.e. esse is beyond empiricism.
Perceive --> Existence (Hallucinations torpedo the test)
Existence --> Perception (Backwards, not a test)


Yes, we infer what is not perceived from our models of the world (or "worldview" to some). That is all we can do, unless we're a solipsist, which treats it all as fantastical, presumably.

Fortunately, we have other humans who can (eventually) cross-correlate or correct any missteps of our model of the universe. In our modern world, we have multiple battles for Truth and this has confounded many people's quest for it, so watch out for the quest for power.

"Can we ever really know the nature or scope of the Universe?". Yes, because we are not alone in our quest for understanding. Besides ourselves, we have YHVH/GAIA, who/which can correct our misunderstandings over time.

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