A phenomenon is the way in which a thing, a fact of the physical world (object, action …), psychic (emotion, thought …) or social (product of social interactions) is manifested to the sensitivity of a living being. Certain phenomena of physics, such as magnetism, ultraviolet light, X-rays, etc. do not affect the sensibility of different living beings in the same way. The word phenomenon comes from the Latin phaenomenon, borrowed from the Greek φαινόμενον, “appearance”, derived from the ancient Greek φαίνω, “to make appear”.
It is contrasted sometimes, notably Emmanuel Kant who has made from the notion a philosophical problem, with the phenomenon as it appears to our mind to what is in itself a truly supposed existent thing (das Ding an sich). For example, I see a tree (phenomenon), but what is really? We do not know anything about it, whether intuitively, scientifically, or metaphysically.
The phenomenon may also oppose noumenon in the sense of Kant, an object that seems to exist but is not perceptible by the senses, although perhaps understandable by the intellect. The noumenon is distinct from the thing in itself in that it is an intellectual object only, which thus does not manifest itself as a phenomenon.
For Kant, “the indeterminate object of an empirical intuition is called a phenomenon.” A phenomenon is the object of an empiric intuition, it appears, to a subject. The phenomenon is what is generally given to the sensitivity of the subjects. The phenomenon thus links an object, from which comes the phenomenon, a subject, which receives the phenomenon, passive, and a manifestation, an apparition, which makes the connection between the object and the subject. Kant opposes the phenomenon to noumenon: phenomena constitute the world as we perceive it, and noumenes reveal a world whose existence is, on the contrary, independent of our experience, the thing in itself. This conception is that of Plato: Plato perceives the phenomenon as the occasional cause that makes us remember (myth of the cave, Phaedo). Plato sees the phenomenon as a copy of the world of Ideas. The empiricism of Berkeley and Hume opposes it. Husserl returns from the empirical tradition to found phenomenology. Bohr uses the concept of phenomenon preferenced to facts to emphasize the importance of the observer.
For Tibetan Buddhism, some of the comments in the Heart Sutra contain a traditional definition of the phenomenon: “Rang gui ngo wo dzinn pèï teun” which means “The phenomenon is the function that grasps what constitutes it as such”. The phenomenon is not a “thing”, it is a function, and more particularly a cognitive function which, in its operation, its operativity, captures what constitutes the phenomenon as such (with its own characteristics). The phenomenon is the representation that the cognitive process that constitutes it operates in itself. The phenomenon, the being, emerges in this operation, it does not exist as an independent reality of the cognitive process that knows it. This is the heart of interdependence, which is mentioned in this Sutra.