Immanuel Kant – Transcendental Idealism

Kant’s Description of the Transformation of Sensations into Experience

Summarizing the argument presented in: Immanuel Kant. Critique of Pure Reason. Originally published as Kritik der reinen Vernunft. 1781. Trans. by Norman Kemp Smith. London: Macmillan, 1929.

Kant defines “transcendental idealism” in the following way: “… Everything intuited in space or time, and therefore all objects of any experience possible to us, are nothing but appearances, that is, mere representations, which, in the manner in which they are represented, as extended beings, or as series of alterations, have no independent existence outside our thoughts. This doctrine I entitle transcendental idealism. The objects of experience, then, are never given in themselves, but only in experience, and have no existence outside it.

(Book II: The Dialectical Inferences of Pure Reason; Section 6: Transcendental Idealism as the Key to the Solution of the Cosmological Dialectic.)

Kant says experience is constructed in three steps. The three steps are summarized below.

Step 1

Kant’s Categories and Principles

Explanation or Comment

Manifold of Intuition

also known as



Sensory Manifold

The manifold of intuition is the ‘faculty’ or ‘functioning capability’ of the mind that does the work in the first step.It is important to note that the first function is asethetic, rather than rational or logical, and occurs prior to consciousness’s awareness of sensory input.
Organizes sensations into spatial and temporal configurations to give “representations” of an “object” According to Kant, experience is not given or passed over to us by our encounter with the world, but is constructed by mental processes. Our conscious imagery of the “world” around us, for instance, cannot be simply our mind’s reflection, like a mirror, of the world.
Is pre-conscious Our mind has more to it than consciousness.

Transcendental Aesthetic

This is the Kant’s name for the principle that drives the first stage. This principle is not taken from the world and is not inside our experience; the principle transcends mental processes and is prior to them.

Step 2

Kant’s Categories and Principles

Explanation or Comment

The Understanding


Analytic of Concepts

It was important for Romantics, after Kant, that intuition and understanding preceded reasoning in the construction of experience.
Organizes “representations” — created by the Transcendental Asethetic in step 1 — into (a) “judgments” and (b) “categories” The Understanding produces experience.

Judgments are logical ways of relating representations, such as deductively and inductively. Categories are the modes of being which the representations present an object as having, such as “quantity” (being one or many), and “quality” (being real, or a negation, or a limit, for instance). Familiar (dichotomous) categories constructed by Understanding are man/nature and subject/object.

Results in consciousness The Understanding is prior to experience and is not derived from experience, but the result of its activity is our conscious awareness of “objects” which we necessarily believe to be of the world external to us.

Transcendental Analytic

Kant’s term.

Step 3

Kant’s Categories and Principles

Explanation or Comment

Pure Reason

Reason is not a mode of experience or a style of experience. Reason is the activity of a principle of mentation.
Organizes the content of the understanding from step 2 into propositions or arguments (e.g., “thinking being is a substance”), according to Transcendental Principles. Reason makes natural science possible.
The Reason, acting on what is passed to it by the Understanding, produces formal knowledge, such as Newton’s laws of motion. Such knowledge is conscious, but not volitional. The activity of Reason in Kant is inexorable; we do not choose what Reason does. We are compelled by the Reason to believe the knowledge it produces is objectively true.

Transcendental Dialectic

Kant’s term points to the manner of his argument. Kant argues that all our logical arguments to demonstrate that there is an objective nature governed by Newtonian laws independently of us, are doomed to self-contradiction. This is a “dialectical” style of argumentation.


Why is Kant’s philosophy of transcendental idealism important for the history of science? Kant “saved” Newtonianism, and thereby saved the scientific basis for the Englightment of the eighteenth century.

In the Critique of Pure Reason, Kant repelled David Hume’s critique of Newton’s philosophy of nature. Newton and the Newtonian party believed that nature had a physical necessity to be constructed in a Newtonian manner. (For an example of this reasoning, see the selection from William Whiston, A New Theory of the Earth [1696].) Hume decisively demonstrated that there is no physical necessity in nature analogous to logical necessity in mathematics. It is possible to imagine that nature might be constructed differently and obey non-Newtonian laws. Hume’s argument threatened the cultural program of the Enlightenment, because the philosophes based their anti-authoritarianism and defense of individual reason on Newtonian science. If Newtonian nature were only contingent, then the Enlightenment’s cultural program could not be necessary, either. Kant responded to this attack on the Newtonian basis of the Enlightenment. Kant demonstrated that our minds construct our experience of nature so that we experience nature as Newtonian; further, we have no choice but to believe that nature is objectively Newtonian in law. He shifted the necessity for Newtonianism from nature to mentation about nature. Nature might not be Newtonian, but we nonetheless are compelled to believe it is by the operation of our minds in constructing exprience.