Kantian Non-constructivism
Kant is not infrequently called a "proto-constructivist," by which is meant that Kant staked out positions that are constructivist in spirit but which preceded the explicit formulation of constructivism by more than a hundred years. I believe that there are good reasons for calling Kant a proto-constructivist, given his insistence upon the exhibition of objects in intuition. I have argued elsewhere (in an unpublished manuscript) that in fact this Kantian focus on exhibition in intuition is the authentic core of constructivism.
Nevertheless, even as a proto-constructivist (a constructivist before constructivism was cool), Kant was far from a thorough-going constructivist. In fact, I just realized today that Kant makes a spectacularly non-constructive argument in his transcendental aesthetic, which lays the foundation for the whole of his philosophy that followed.
Near the beginning of the Critique of Pure Reason, when Kant gives an exposition of the concepts of space and time in the transcendental aesthetic, Kant offers parallel formulations of the two concepts. Here is Kant's exposition of space:
Space is a necessary a priori representation, which underlies all outer intuitions. We can never represent to our- selves the absence of space, though we can quite well think it as empty of objects. It must therefore be regarded as the con- dition of the possibility of appearances, and not as a determina- tion dependent upon them. It is an a priori representation, which necessarily underlies outer appearances.
And here is Kant's exposition of time:
Time is a necessary representation that underlies all intuitions. We cannot, in respect of appearances in general, remove time itself, though we can quite well think time as void of appearances. Time is, therefore, given a priori. In it alone is actuality of appearances possible at all. Appearances may, one and all, vanish; but time (as the universal condition of their possibility) cannot itself be removed.
In his twin expositions of space and time, Kant asserts that, while we cannot imagine objects outside space or time, we can nevertheless imagine space and time without objects. Kant makes this assertion, but he does not demonstrate how space or time without objects can be constructed, not does he exhibit empty space or empty time in either sensory or intellectual intuition. Here the Kantian insistence upon exhibition is utterly absent.
I can still remember how I was struck by this passage the first time I read it. It has stayed with me all these years. Philosophers today consider the ideas of empty space and empty time to be problematic; indeed, the defense of these concepts has become a minority (if not a marginal) view. (In the interest of full disclosure, I will state here I find the concepts of empty space and empty time to be perfectly legitimate, but even in so saying I know that it is a minority view made all the more marginal by the most common interpretations of relativity theory.)
C. S. Pierce's comment on his study of Kant is quite interesting in this context, so I will quote Pierce at some length:
The first strictly philosophical books that I read were of the classical German schools; and I became so deeply imbued with many of their ways of thinking that I have never been able to disabuse myself of them. Yet my attitude was always that of a dweller in a laboratory, eager only to learn what I did not yet know, and not that of philosophers bred in theological seminaries, whose ruling impulse is to teach what they hold to be infallibly true. I devoted two hours a day to the study of Kant's Critic of the Pure Reason for more than three years, until I almost knew the whole book by heart, and had critically examined every section of it. For about two years, I had long and almost daily discussions with Chauncey Wright, one of the most acute of the followers of J. S. Mill.
The effect of these studies was that I came to hold the classical German philosophy to be, upon its argumentative side, of little weight; although I esteem it, perhaps am too partial to it, as a rich mine of philosophical suggestions. The English philosophy, meagre and crude, as it is, in its conceptions, proceeds by surer methods and more accurate logic.
COLLECTED PAPERS OF CHARLES SANDERS PEIRCE, EDITED BY CHARLES HARTSHORNE AND PAUL WEISS,VOLUME I, PRINCIPLES OF PHILOSOPHY, CAMBRIDGE, HARVARD UNIVERSITY PRESS, 1931
Despite many years of study of one of the most difficult books ever written, Pierce found Kant to be "of little weight" when it came to argument. Well, I will admit that the argument of the transcendental aesthetic is pretty weak, and I say this on general principles, and not because it is a non-constructive argument. However, I can imagine that Pierce, with his "pragmatic" turn of mind, may have discerned the non-constructive core of Kantianism and found it to be a weak argument.