hool, to which he
remained true for a considerable period as a teacher and writer (till about
1760), although at the same time he was inquiring with an independent
spirit, Kant was gradually won over through the influence of the English
philosophy to the side of empirical skepticism. Then--as the result, no
doubt, of reading the _Nouveaux Essais_ of Leibnitz, published in
1765--he returned to rationalistic principles, until finally, after a
renewal of empirical influences,[1] he took the position crystallized in
the _Critique of Pure Reason_, 1781, which, however, experienced still
other, though less considerable, changes in the sequel, just as in itself
it shows the traces of previous transformations.

[Footnote 1: Cf. H. Vaihinger's _Kommentar zu Kants Kritik der reinen
Vernunft_, vol. i., 1881, pp. 48-49. This is a work marked by acuteness,
great industry, and an objective point of view which merits respect. The
second volume, which treats of the Transcendental Aesthetic, appeared in
1892.]

It would be a most interesting task to trace in the writings which belong
to Kant's pre-critical period the growth and development of the fundamental
critical positions. Here, however, we can only mention in passing the
subjects of his reflection and some of the most striking anticipations and
beginnings of his epoch-making position. Even his maiden work, _Thoughts on
the True Estimation of Vis Viva_, 1747, betokens the mediating nature of
its author. In this it is argued that when men of profound and penetrating
minds maintain exactly opposite opinions, attention must be chiefly
directed to some intermediate principle to a certain degree compatible with
the correctness of both parties. The question under discussion was whether
the measure of _vis viva_ is equal, as the Cartesians thought, to the
product of the mass into the velocity, or, according to the Leibnitzians,
to the product of the mass into the square of the velocity. Kant's
unsatisfactory solution of the problem--the law of Descartes holds for
dead, and that of Leibnitz for living forces--drew upon him the derision
of Lessing, who said that he had endeavored to estimate living forces
without having tested his own. A similar tendency toward compromise--this
time it is a synthesis of Leibnitz and Newton--is seen in his
_Habilitationsschrift, Principiorum Primorum Cognitionis Metaphysicae Nova
Dilucidatio_, 1755, and in the dissertation _Monadologia Physica_, 1756.
The f