In Note III to §13 of the Prolegomena, Kant seems to be answering some critics that have compared his transcendental idealism to the philosophies of Descartes (at least the skeptical part of it) and Berkeley.

In the very end of it, he writes this:

But if it is an in fact reprehensible idealism to transform actual things (not appearances) into mere representations, with what name shall we christen that idealism which, conversely, makes mere representations into things? I think it could be named dreaming idealism, to distinguish it from the preceding, which may be called visionary idealism, both of which were to have been held off by my formerly so-called transcendental, or better, critical idealism. (Ak. IV:293-94)

The German original reads:

Wenn es aber ein in der Tat verwerflicher Idealism ist, wirkliche Sachen (nicht Erscheinungen) in bloße Vorstellungen zu verwandeln: mit welchem Namen will man denjenigen benennen, der umgekehrt bloße Vorstellungen zu Sachen macht? Ich denke, man könne ihn den träumenden Idealism nennen zum Unterschiede von dem vorigen, der der schwärmende heißen mag, welche beide durch meinen sonst sogenannten transzendentalen, besser kritischen Idealism haben abgehalten werden sollen.

I understand that Kant refers to Berkeley when talking about the visionary (schwärmender) idealism, but what is the dreaming (träumender) idealism? Is he talking about Descartes? Is he talking about some misinterpretation critics made of his transcendental idealism?

1 Answer 1


This is explicitly answered in the introduction to the Cambridge Edition written by Gary Hatfield, in the comments on the structure of the work, where he gives a short summary of the main text. He writes on §13, note III:

Kant’s position does not turn bodies into illusion, but it explains how pure mathematics can apply to bodies (and so, how geometry can be taken as describing the properties of bodies in space), and it prevents transcendental illusion as found in the antinomies; hence, his transcendental or critical idealism is to be distinguished from the empirical or dreaming idealism of Descartes and the mystical or visionary idealism of Berkeley (bolded mine, p. xxix)

Thus, Kant refers to Descartes, just as you already surmised. This is probably as, per Descartes, the insights into (the fabric of) reality come to you by introspection and the analysis of your inner representations of the empirical world, ultimately taking our representations and thinking as absolutely accurate for (and indistinguishable from) outer objects and ultimately metaphysical reality. That way, our representations are turned into things in themselves and metaphysical reality as there is no place (nor a need) for an epistemic difference between them in Descartes' philosophy.

Therefore, Kant has to delimit his own philosophy from that even if representations as one source of knowledge - empirical knowledge, not metaphysical knowledge - are part of his own "idealism". His own philosophy is all about distinguishing between these different kinds of knowledge (empirical and pure) and the methods of how to ascertain them, so he needs to argue against simplifications like "oh but THAT part is just like in Descartes!" Hence, Hatfield can write about Descartes' idealism as both empirical and dreaming - a pair that otherwise would not make any sense - since the content is empirical (just like in Kant) but the epistemic object is indistinguishable from the representations given by a dream, which makes critical metaphysics impossible in Descartes.

Effectively, Kant dismisses Descartes' immediate knowledge about truth simply by "seeing the light" here and highlights the fact that Descartes made it impossible to distinguish between true and untrue metaphysical statements out of methodological reasons. Descartes may be skeptical but only because he tries to argue that even the fiercest skepticism gives us no reason to question the accurate correspondence between perception (representation) and metaphysical object. In other places Kant argues that if we assume that, it ends up in an identity of representation and object since we lack the epistemic means to distinguish them.

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