If one has an ineffable experience or, more simply, an epiphany related to the ineffable dimension, can he communicate it to other people in principle (that is, through a communication that exists on a physical level)?
Note 1) I consider thoughts not ineffable.
Note 2) Perhaps, I am facing the same problem described in the question while writing it...
Has this problem been already discussed in philosophy?
Yes, but not straight-forwardly; it's a spark that might strike - or not.
To take a simpler example, consider music: two persons may listen to the same piece of music, and it is then right to say they have heard the same sounds; but one might have felt or been transported in a deeper way than the other, who heard merely the play of sound.
This, in fact is one of the functions of sacred art; traditionally oral poetry or music; but it requires receptivity, and for that - rare and temperamental; which is one reason it's surrounded by rituals of association and evocation - a kind of sympathetic magic.
There's an echo of this in the last paragraph of Joyce's A Portrait of an Artist where the young Stephen Dedalus on the cusp of manhood has an epiphany, or rather Joyce is communicating his:
The spell of arms and voices, the white arms of roads and the promise of close embraces and the black arms of tall ships that stand against the moon their tale of distant nations. They are held out to say: we are alone - come. And the voices say with them we are your kinsmen; and the air is thick with their company as they call to me, their kinsmen, making ready to go, shaking the wings of their exultant and terrible youth.
The use of language here is lyrically complex, rhythmic with repitition and alliteration; combining symbols of magic, adventure, madness, eros and intimations of mystery - together with profane, sacred and the sublime and this in final stretch of everyday prose so it stands out like some low luminous flame.
Frank Sneed addresses this in his work Theology and Sanity. In it, he makes the distinction between imagination and intellect, and says that there are metaphysical ideas that one might not be able to "imagine," but which are nonetheless the rational conclusion of the intellect.
One can also see this addressed in other theological works that look to reason as their basis, such as Aquinas. Aquinas goes through painstaking detail to describe and justify his metaphysical conclusions.
One also finds this in a number of other works - much of (neo-)Platonism is based on their being a real metaphysics that one can know about and communicate about.
To repeat, this question is hardly a naive one. And, yes, it has been discussed, though perhaps not in an entirely satisfactory way.
The above reference to Wittgenstein is apt. We can "communicate" by pointing to objects and triangulating. But how do we "communicate" ideas about pure sensations with no external object, like "pain"? Or "moods" Or even "sensations"? Only by secondary observation of behaviors, including language behaviors?
I do not think philosophy can resolve such higher-level forms of skepticism. At least not as bounded by "physics." So, as Hegel said, you can't evade metaphysics. You must import the "meta" back into physics.
And where did we last leave the "physicist"? With quantum entanglement and Einstein's "spooky action at a distance." How can we communicate metaphysical concepts? I suspect because "communication" is prior to "human being." We are "in communication" long before we "talk about it" or have a "physics" of experience.
Philosophy, in my view, neglects the "in utero" continuum of all "physics."
I would take up the younger Wittgenstein, here, and say no.
At their purest, forms of language merely evoke a 'picture' of an experience, which we can ordinarily converge on because of shared experience or shared mental and physical constitution. There are certainly quite ordinary physical notions that require that purity of communication for real understanding, and therefore cannot readily be communicated directly, but can only be alluded to, until one shares the same basic formative experiences that evoked it in others.
I cannot explain the rush of adrenalin to you, for instance, unless you have experienced enough similar events to form a frame of reference. Most of us have that experience from infancy, but some odd people, say a narcoleptic who blacks out when the rest of us would get an adrenalin rush, just will not ever understand its significance.
An autistic may never really understand the feeling evoked in a neuro-normal person by a child's smile. So their interpersonal motivations may lack a certain natural ease.
I am assuming your notion of a 'metaphysical' experience goes beyond that, or it would simply not need a name. (Although 'metaphysical' is surely not the right name, and may insult some here.)
At the same time, humans share a lot of underlying experiences of which they are fully unaware. So, for instance, we often find mythological tropes in dreams or hallucinations. We may understand the imagery others experienced generations ago in pure distress, under some kind of drug, or vice versus. So it is never a waste of time to try. Although you cannot communicate your experience by the ordinary process of triangulation between impressions, you may evoke something adjacent to it in someone, in which case it still serves a purpose.
You seem to use metaphysics in a New Age sense, which isn't how philosophy defines it. To get an idea of how philosophy defines metaphysics, check out this Wikipedia page.
With that said, is it possible to communicate a metaphysical experience? Let's break this down:
(1) is there any such thing as metaphysics? Some philosophers reject metaphysics or at least the attempt to talk about it. Hume, Carnap, Ayer and Wittgenstein all fall into this camp.
Among those who think metaphysics exists or that we can talk about it, how many think (2) is plausible? This depends on how they view human experience. Those who hold that humans are material beings in a material reality would say that our experience arises from material interactions. This would seem to rule out metaphysical experiences which would require "stepping outside" of material reality to see the foundations.
What if instead of experiencing the metaphysical, you infer it? Well logic is a symbolic, well structured process that proceeds from agreed-upon premises via well-defined rules to conclusions. By definition, this process can be communicated, and is communicated every day.
Ok, well what if you hold (1) and (2), how does (3) fare? Now we're into speculative territory. I doubt (3) would hold as your experience would likely be ineffable.
Ineffability is a big problem. To see what a challenge it is, imagine trying to explain the color red to someone who is blind from birth. When I tell someone that a dish was salty, I can only say this because I assume they have experienced saltiness and thus can attach their experience to that label. However, that label does nothing to communicate the experience itself. In short, language only works because there's a shared base of experience we can draw upon, which allows us to bypass the ineffability problem. With (3) you wouldn't have this common ground.
At this point, you might have to take a page out of the mystics' playbook and try to explain by analogies or get people to experience what you experienced.
For me, this is a semantic problem. "Ineffable" is a word that by definition describes something that can not be described with words. If you are asking whether things that can't be described by words... if they can be communicated by means other than words, then I would have to think about it. But asking if something ineffable can be described by words is like asking if unicycle can have two wheels.
