I've been studying Kant's philosophy recently and I haven't been able to get something straight.

Quick question here: How does Kant's distinction between phenomena/noumena apply to ideas and thoughts? Are there such things as thoughts or ideas "in-themselves" prior to being articulated? If not, then are they categorised as phenomena?


  • Ideas (transcendental logic) are not perceived by means of the senses (transcendental aesthetic). So, they are not phenomena. And in consequence, they have no noumenal correspondence.
    – RodolfoAP
    Sep 16, 2021 at 18:06
  • 1
    It does not apply at all. Ideas and thoughts studied empirically, as part of psychology, are not Kant's concern. And as functions of transcendental faculties they are part of the subject, not its objects, like phenomena and noumena.
    – Conifold
    Sep 16, 2021 at 23:36
  • @Conifold. - According to Kant, external objects are transcendentally internal , though they are empirically external. Sep 18, 2021 at 16:33

1 Answer 1


The phenomenal/ noumenal distinction is not identical to the external/ mental one.

Kant takes nature to be the realm of phenomena, and phenomena to be all that appears in space and time. But our mental states appear in time. So our mental states are phenomena; and they are subject to natural laws ( meaning that psychollogy is part of the science of nature, albeit Kant admits it cannot really be made scientific, due to the difficulty of mathematizing mental phenomena).

See : methodology of pure reason in CPR and more specifically the architectonics of pure reason.

Since there is no phenomenon whitout an in-itself reality that appears , our mental states refer to a thing in itself, in the same way as appearing matter ( in the external/ spatal world ) refers to a thing in itself.

Though we have no cognitive access to the essence of this thing in itself that is " beyond" our mental phenomena, we are aware of its existence by the fact that some of our thoughts feature a kind of spontaneity, they are not passive/ receptive ( as are intuitions) but rather they are active: these phenomena are what we call thoughts ( intellectual states and acts), concepts, synthetic acts.

This is for the cognitive side of our mental life. On the appetitive side, spontaneity also appears in the form of will, and more specifically moral will ( act of the will that responds to no sentitive motive, but only to the the pure respect for moral law).

As to the question " are ideas noumenal" it is somewhat ambiguous. Ideas have 2 sides : (1) they are mental items ( this is their formal reality as says Descartes) (2) they have a content and an object. As mental phenomena, ideas are not noumenal, they exist in time " in our heads/ minds", they are a species of representation ( see kant's typology of representations at the beginning of the Transcendental Dialectics in CPR). But their objects are ( alledgedly) noumenal , or, at least , they are beyond the limits of all possible experience.

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