The Old Man 411in the Analytic of Principles of the first Critique. Presumably, they would
also have to be more specific than those that he had identified in the Meta¬
physical Foundations of Natural Science. Some of his remarks suggest this,
but some of the titles suggest a more ambitious enterprise, namely, the
formulation of the a priori principles of physics itself. Perhaps not sur¬
prisingly, Kant did not succeed.
Roughly put, Kant approached the filling of this still-remaining gap in
his system, that is, the lack of a metaphysics of nature or natural science,
in the following way. He postulated a kind of ether or caloric matter, which
filled up the entire universe and penetrated all bodies equally. This ether,
or original matter, was accordingly not subject to any change of place. Kant
also wanted to show that ether, as original matter, is not a merely hypothet¬
ical principle. It is indeed the original moving force. Without it, there would
be neither objects of sense nor any experience. He used this ether to ex¬
plain all other moving forces, and, in what was to be the first part of the
book, he tried to give an account of them in accordance with the table of the
categories. In the second book, he intended to formulate the system of the
world. What has come to us concerns mostly the first part.^107
Kant worked hard on filling a perceived gap between the foundations of
the metaphysics of nature and physics beginning in 1796, but a solution
evaded him. The solution of postulating ether as an a priori principle sug¬
gested itself only after "several years," namely "in 1799." This solution is,
according to Förster "reflected in the unique status Kant now assigned to
the concept of ether, which had initially been introduced in the Opus pos-
tumum to explain a number of physical phenomena."^108 Ether, as hyposta-
tized space, which is all-penetrating, all-moving, and permanent, became
now the a priori principle that provides systematicity to physics. This "so¬
lution" would never have occurred to the critical Kant. Ether was a kind
of matter, and no matter of any kind could be for him a priori. Indeed, a
priori matter would have been a contradiction in terms for the critical Kant.
Matter always was and had to be a matter of experience. Yet, now ether "as
material for a world system, [was] given not hypothetical but a priori" sta¬
tus.^109 This is a contradictio in adjecto, at least from the point of view of crit¬
ical philosophy.^110 Kant himself noted that a proof that establishes this kind
of matter "appears strange; for such a mode of inference does not seem at
all consistent or possible."^111 Yet he goes on to outline such a proof.
It is perhaps not surprising that Kant himself almost immediately real¬
izes that this does not amount to a solution.^112 (What is surprising is that
he would ever have found it worthy of writing down.) What he substitutes