Despite his brilliance in reasoning, Kant went down into the magma of some confusion of ideas on defining phenomenon and empirical intuition.
The German philosopher defined phenomenon this way:
"The undetermined object of an empirical intuition is called phenomenon." (Kant, Critique of Pure Reason, Calouste Gulbenkian Foundation, Portuguese edition, page. 61).
It is obvious that Kant distinguishes between phenomenon - for example, chair - and intuition of the phenomenon - to see or to touch the chair, in this example. But what is the phenomenon? In Kant´s theory, the phenomenon is composed by empirical intuitions, and essentially, by pure intuitions: figure and extension. And by some a priori concepts.The phenomenon, such as bicycle, dog or cloud is nothing in itself: it's just a figure without color, without sound, without smell, without defined matter, enclosed in a space that is unreal, as space is only a priori intuition. Kant is an ontological idealist: the material objects do not exist outside the human mind, they are complexes of sensations and three-dimensional intuitions. There is not, for example, horse-noumenon and horse-phenomenon, and this is not perceived by the great majority of academic teachers and philosophers. The phenomenon horse is only representation of something unknowable. Kant wrote:
«Thus, when I separate from the representation of a body what understanding thinks about it, such as substance force, divisibility, etc., and also what belongs to the sensitivity such as impenetrability, hardness, color, etc., something still remains of that empirical intuition: the extension and figure. These belong to pure intuition which exists a priori in the spirit, even independent of a real object of the senses or of a sensation, as a simple form of sensibility. »(Kant, Critique of Pure Reason, Calouste Gulbenkian Foundation, p. 61).
Now, this text dismantles the real object of the senses or phenomenon, showing that it is no more than a complex of formal intuitions (figure, space) and concepts. The color, the hardness do nor belong to the bike: they are sensations, empirical intuitions, illusionary modes to perceive this vehicle which is a phenomenon. The unitary character of the bicycle as cluster of metal parts is a concept of the understanding, it is the category of substance and accident, is not on the bike. And the problem arises: when we see a bike that is beyond our physical body but within our mind that surrounds it and forms the space, we have a set of empirical intuition and sensation (colorvision, feeling of hardness of the metal or of the saddle, etc.) of a phenomenon that is reduced to the geometric empirical intuitions (the bicycle lines), an indeterminate matter (something that has no color, no weight, no smell, no ductility) and concepts (only substance divisible into parts).
Thus, the notion of empirical intuition is treated ambiguously in Kant: it is the matter of the phenomenon ( "I give the name of matter to which in the phenomenon corresponds to the sensation" says Kant; but an absolutely abstract matter, as the Hyle of Aristotle, because the color , the smell, the sound, the feeling of hardness are mere sensations, appearance), the objectively "real to us" and is the perception of matter of this phenomenon, perception that already includes color, sound, smell, hardness, etc. You must note also that, following the theory of primary and secondary qualities of Descartes, Kant establishes two types of empirical intuition as perception, distinguishing sensation (subjective quality, illusory) from intuition (objective quality):
«The pleasant taste of a wine does not belong to the objective properties of this wine,thus to an object even considered as a phenomenon, but belongs to the special nature of the sense of the subject who relishes it. The colors are not the property of bodies, to the intuition of which they relate, but simply changes of the sense of vision of the that is affected by the light in a certain way. The space on the contrary, as a condition of outer objects, necessarily belongs to the phenomenon or to the intuition of the phenomenon. " (Kant, Critique of Pure Reason, Calouste Gulbenkian Foundation, page 69, footnote; the highlight in bold is my own).
In this case, the flavor and the color of the wine would be the subjective intuition and the wine itself would be the objective intuition and the phenomenon. But what is the wine without color or taste?
In short, the contradiction of Kant is that he expels the phenomenon to the field of sensations (subjective intuitions of the phenomenon) and to the field of concepts what really characterizes it: the color, the taste, the hardness, the concrete matter that it is made (in the case of the tree: wood and leaves), transforming the phenomenon in a ghost figure, a meatless skeleton, pure form in a given time.
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