Suppose a multitude of people all recount similar experiences. They describe seeing a cup on a table or observing the Moon in the sky. Each person reports their own subjective experience of perceiving these phenomena. Based on their reports, there seems to be agreement or consensus among the individuals about what they claim to have observed. This begs the question: does this collective agreement imply an objective reality? In other words, can we conclude definitively that there is indeed a cup on the table or that the Moon is in the sky?

We can also ponder the question in the reverse direction: if something is objectively the case, does it follow that people will necessarily intersubjectively agree on it being the case?

Put differently, does the alignment of subjective reports equate to objectivity? If not, how can we distinguish between something being objectively the case and a bunch of individuals intersubjectively agreeing that something is the case?

Symbolic Representation of the Question

Let ISA(P, X) denote a set of individuals P who intersubjectively agree that X is the case.
Let O(X) denote that X is objectively the case.
Let A => B represent A logically entailing B.
Let A <=> B denote that A is logically equivalent to B.

Are the following statements true?

  • ISA(P, X) => O(X), for some set of individuals P (with possible conditions on P).
  • O(X) => ISA(P, X), for some set of individuals P (with possible conditions on P).
  • ISA(P, X) <=> O(X), for some set of individuals P (with possible conditions on P).

Note: This question was inspired by the discussion under this answer.

  • I would upvote the question. But I don't find the logical analysis compelling. Specifically, Let O(X) denote that X is Objectively the case. This can be asserted or believed by a subject, but it could not be verified, without evoking the perceptions and evaluations of at least one subject. So there would have to be subjective belief or intersubjective agreement to assert O(X) unless it is taken as a mere abstract concept. Even the abstract concept depends on the existence of subject(s). Commented Apr 25 at 17:44
  • 4
    It should be rather obvious that, under realism, a bunch of individuals intersubjectively agreeing on something does not entail its truth, unless one of the individuals is omniscient God himself. It may be a reasonable guide to the truth, assuming the individuals follow truth-oriented practices and the subject of agreement is amenable to their means of inquiry. Existence of verification-transcendent truths is the main point of controversy between realists and anti-realists.
    – Conifold
    Commented Apr 25 at 17:45
  • @SystemTheory I'm happy to receive answers proposing a more robust formalism.
    – Mark
    Commented Apr 25 at 19:13
  • Analogically, it's like the difference between potential and actual infinity. The latter is an ideal, and while conceptually useful, is a sleight of hand with hidden normative undertones.
    – J D
    Commented Apr 26 at 1:08
  • Your relations O and ISA are not logically connected, so none of your statements are possibly true. Note that we can restrict the discussion to statements about natural numbers and still pick up Tarski's toolkit; it's unlikely that any sort of quibble about reality or realism is going to work, since we can talk solely of abstracta.
    – Corbin
    Commented Apr 27 at 1:12

6 Answers 6


The dispute about realism travels through a spectrum of views.

Most people, before engagement with philosophy of science, hold by direct realism (DR) -- that we can and do discern the reality of our world through direct perceptions. That apples are red, the sky is blue, and snow is cold. The objective world out there is directly knowable by us.

Indirect realism (IR) starts with the presumption that our perceptions (or more commonly today our experiences) are real, and we can only infer the reality of our world indirectly, and with some uncertainty. Our perceptions or experiences are still held to be confirmed through direct realism.

The work of neuroscience and the illusionist school of philosophy of mind has brought the trustworthiness of our perceptions under suspicion, and also the trustworthiness of our experiences. While the delusionists over-extrapolate off this data to call for throwing all of it out, a pragmatic alternative is to treat both perceptions and experiences as constructed inferences by our unconsciousness. This is two more options, illusionism about our interior states (IL) and pragmatism that all of our external and internal hypotheses are at least useful engineering approximations to reality (PR).

One can take this suspicion of the validity of our data a step further, and give up on the idea of realism altogether. There are variations of anti-realism, the two most widespread being pure empiricism (all we can say is that we have the data and models) and instrumentalism (the data and models are all we can really treat as valid/real) (I will label these IN).

One can take the anti-realism a step further, and deny that the external world is real at all, and arrive at idealism (ID).

The spectrum of realisms then ranges from:

DR -> IR -> PR -> IL -> IN -> ID

DR, IR, PR, and IL hold that matter is real. DR, IR, PR, IN, and ID hold that experiences or perceptions are real. DR holds that we can have certainty about matter. DR, IR and ID hold that we can have certainty about experiences.

I at least, and most philosophers of science, consider the differences between direct and indirect perceptions, and the degree of our ability to infer to an ontology, to have important considerations for our overall worldview, epistemology and ontology -- and the differences between these viewpoints to be a big deal.

As a pragmatist, I am still in the range of the spectrum considered realist. I consider that we cannot ever access "objective" reality -- and that degrees of evidence short of "intersubjective consensus supported by reams of science" are actually key to valid inferences to that reality. After all, none of our perceptions or experiences can be verified "scientifically" yet we can still make valid inferences about our selves, and our perceptions.

In the dispute you reference, Speakpigeon was advocating for the classic IR position, but with a linguistic shift where one redefined external intersubjective consensus as "objective". I objected to two aspects of this -- that we have good evidence to think that internal knowledge is less reliable than he was assuming -- and that the consequence of our NOT having access to objectivity is actually an important point that should inform our epistemology, and should not be obscured in a linguistic reshuffle. I argued the second point because I think the epistemic implications of this dispute are highly relevant to our worldviews.

Note, that most non-philosophers tend to be arguing the POVs on the left side of that spectrum, while serious philosophers tend to be arguing for the various views on the right side of that spectrum. This is why Conifold's comment implies that realism vs antirealism is where the philosophic action is, rather than in the dispute between two realists such as Speakpigeon and myself.

Now, trying to answer your questions from the POV of a pragmatist in the middle of this spectrum:

does this collective agreement imply an objective reality?

No. We have a history of collective agreements that have been overturned. So no, one cannot be certain of objective reality just because our current views have a consensus on a question.

if something is objectively the case, does it follow that people will necessarily intersubjectively agree on it being the case?

Again no. We had no agreement on the elements, before chemistry advanced a few hundred years ago. And the atomic theory of the elements is a far more recent discovery. We think these are objective reality, but for most of our history they have not been intersubjective consensus.

how can we distinguish between something being objectively the case and a bunch of individuals intersubjectively agreeing that something is the case?

We can't. We don't have access to reality, all we can do is make our best guess inferences based on our steadily improving database.

  • 1
    Hermann von Helmholtz performed experiments and developed the theory of Unconscious Inference. To experience this I place my thumb in front of the moon. This shows that my thumb is larger than the moon in my visual field. By contrast I automatically perceive my thumb as small and nearby and the moon as large and far away. Because the inference of the size, location, and speed of objects is not conscious Helmholtz describes this as an unconscious inference. Further, if I have a model of neurons that are not conscious, but somehow generate unconscious inferences, the neural model is conscious! Commented Apr 26 at 18:57
  • @SystemTheory How would a model of neurons generating inference be conscious? We know that 99+% of the actual inferences that neurons generate are unconscious, and most of our and our math's modeling is unconscious, why would a model of neurons somehow be conscious?
    – Dcleve
    Commented Apr 27 at 16:10
  • What does unconscious represent? Freud argues it is the conscious distinction between known (Conscious) and unknown (Unconscious). To me the unconscious, as used by Sigmund Freud, is a generic word for The Great Mystery. Freud rejects God as The Great Mystery. But he argues that the Conscious ego stands in relation to The Unconscious. Freud says conscious ego gains knowledge of unconscious inner drives (id) and unconscious external reality (reality). But the models of neurons, nervous system structures, biological ego functions, inner drives, and external reality are fully conscious! Commented Apr 27 at 16:57
  • @SystemTheory -- System 1 of thinking fast and Slow is not conscious, and DOES neural processing. Why would you think that a MODEL of this processing would be conscious, when the processing itself is not.
    – Dcleve
    Commented Apr 27 at 19:58
  • Do you think it is possible to discuss the actual unknown or unconscious? If it is unknown (unconscious) I cannot describe it. I can only describe models that arise and become conscious. Commented Apr 27 at 20:41

I'm going to naively assert that the scientific method assumes a straightforward answer: intersubjective agreement is a useful but imperfect means for finding objective truth.

does this collective agreement imply an objective reality?

It is potential evidence. If there is a testable counter-hypothesis then we need to consider that the collective agreement could be wrong.

if something is objectively the case, does it follow that people will necessarily intersubjectively agree on it being the case?

Not automatically and absolutely. But if there is a gap, it should be possible to explain the discrepancy with sufficient investigation. For example there are many common optical illusions that can be explained. In those cases, we know why people might agree on something they observe but be objectively wrong.

how can we distinguish between something being objectively the case and a bunch of individuals intersubjectively agreeing that something is the case?

By coming up with alternative, testable theories and using these to make new observations that might support or disprove what people previously agreed on. Many major scientific breakthroughs are examples of this. Everyone agreed that the sun moved in circles around the earth until it was proven otherwise. Objectively the Earth was never stationary, but for a long time everyone perceived it that way and were aware of no evidence to the contrary.

  • Brian --I will suggest a few additional complexities to take account of with this answer. The Quine-Duhem thesis shows that one can never "prove" that the sun does not go around the earth. What we can and did do, is show that the solar-centric model to be predictively more useful, because it is not encumbered with so many multitudes of kluge epicycles that were needed to patch the Pythagorean model as our observations found more and more issues. But model power and congruence is not "proof".
    – Dcleve
    Commented Apr 25 at 21:19
  • Also, Popper's attempted to show to show that, despite likely being wrong based on the history of so much of our science being overturned, that our current science is less wrong than prior science. This concept of a gradual approach to truth he called verisimilitude was demonstrated to be logically flawed. The assumption of verisimilitude is behind pragmatic stepwise science, but we cannot logically justify this.
    – Dcleve
    Commented Apr 25 at 21:23
  • @Dcleve Infact the claim is stronger: the "objective" evidence that all humans have had for as long as they have existed is that The sun goes round the earth. Its just that at some point most people stopped believing their sensory evidence and started believing the authority of "scientists:
    – Rushi
    Commented Apr 27 at 7:17

What's the difference between objectivity and intersubjective agreement?

When different people arrive at an intersubjective agreement, they say it is objective.

The expression "intersubjective agreement" is only used by specialists. Everybody else just say objective, but with the same sense.

The idea that the two need to be distinguished comes from the specialists who are still chasing the wild goose of "absolutely objectivity".

  • 1
    Well, actually they don't have say it's objective. If we agree that there is a border between our countries, and here is US and here is Canada, it doesn't mean we think that US and Canada are objective realities. They are just agreements. A little example - USSR disappeared the very moment when three people put signatures on paper in Belarus in 1991. Were they powerful mages that could destroy the biggest country with a pen and 3 second? No, because any country is just an agreement. And we know it if we are clever enough.
    – Groovy
    Commented Apr 26 at 17:00
  • Yet, agreement alone isn't enough.. There is agreement, but also, evidence..
    – CriglCragl
    Commented Apr 27 at 0:27
  • @Groovy "it doesn't mean we think that US and Canada are objective realities." Sorry, but 'It' never ever means anything by itself. We do. It is precisely because you can specify countries in terms which we can all agree on that we think of them as objective realities. Things we think of as objective realities may disappear. The sun goes does over the horizon and disappear. People die and disappear. If your theory was true, you would have to say that only reality as a whole is objective, which is just absurd. Commented Apr 27 at 10:56

enter image description here

Each circle A, B, C represents the knowledge of a subject. If there does not exist knowledge of subject(s) then there are no circles. The attributes of reality, of what exist independent of the knowledge of any subjects, would map to a blank white space in this representation.

Each subject forms ideas or concepts of what does or does not exist independent of the mind of any subject! The term "real" or "reality" may refer to the idea or concept of what items are thought to exist independent of the minds of subjects. These ideas or concepts or beliefs exist in the mind of a subject or subjects not outside the mind.

No subject has knowledge of what exists outside their mind or outside the minds of others. The idea or concept of reality, of what exists independent of the mind, occurs in the mind. There is a blank white space in the diagram illustrating that objective reality is empty or void outside the circles. Objective reality is meaningless in the absence of the knowledge of subjects.


Look at this from physics point.

A key principle in physics is that objective reality should be independent of any individual observer's subjective experience or perspective. The existence of an objective, physical world "out there" is an implicit assumption that underlies the scientific method.

From this viewpoint, the fact that multiple observers subjectively report similar experiences, like seeing a cup on a table, does provide corroborating evidence for an objective phenomenon. However, it does not definitively prove objective reality on its own. perceptions and subjective experiences can be influenced by various cognitive biases, sensory limitations, and shared cultural conditioning. So pure intersubjective agreement is not enough - objective measurement and empirical tests to rule out alternative explanations are required.

Physics relies on precise instrumentation that can quantify and measure phenomena independently of human perception. For example, detecting the presence of the moon is not just about seeing it, but measurements of its gravitational effects, reflected light spectra, orbital dynamics, etc.

  • objective measurement - doesn't this beg the question, because it assumes that the measurement is objective? How do we know it is objective?
    – Mark
    Commented Apr 26 at 22:21
  • en.wikipedia.org/wiki/Consilience "There is nothing you can see which is not a flower, there is nothing you can think which is not the moon" - Basho
    – CriglCragl
    Commented Apr 27 at 0:29

Any objective statement has to be made intersubjectively. So any objective statement is also an intersubjective statement. But the converse does not follow. An intersubjective statement need not be objective.

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