has exercised and continues to exercise must be ascribed to this characteristic feature in the training of its great author.
The early writings of Kant are almost without exception on questions of physical science. It was only by degrees that philosophical problems began to engage his attention, and that the main portion of his literary activity was turned towards them. The following are the most important of the works which bear directly on physical science.
1. Gedanken von der wahren Schätzung der lebendigen Kräfte (1747); an essay dealing with the famous dispute between the Cartesians and Leibnitzians regarding the expression for the amount of a force. According to the Cartesians, this quantity was directly proportional to velocity; according to their opponents, it varied with the square of the velocity. The dispute has now lost its interest, for physicists have learned to distinguish accurately the two quantities which are vaguely included under the expression amount of force, and consequently have been able to show in what each party was correct and in what it was in error. Kant's essay, with some fallacious explanations and divisions, criticizes acutely the arguments of the Leibnitzians, and concludes with an attempt to show that both modes of expression are correct when correctly limited and interpreted.
2. Whether the Earth in its Revolution has experienced some Change since the Earliest Times (1754; ed. and trans., W. Hastie, 1900, Kant's Cosmogony; cf. Lord Kelvin in The Age of the Earth, 1897, p. 7). In this brief essay Kant throws out a notion which has since been carried out, in ignorance of Kant's priority, by Delaunay (l865) and Adams. He points out that the action of the moon in raising the waters of the earth must have a secondary effect in the slight retardation of the earth's motion, and refers to a similar cause the fact that the moon turns always the same face to the earth.
3. Allgemeine Naturgeschichte und Theorie des Himmels, published anonymously in 1755 (4th ed. 1808; republished H. Ebert, 1890). In this remarkable work Kant, proceeding from the Newtonian conception of the solar system, extends his consideration to the entire sidereal system, points out how the whole may be mechanically regarded, and throws out the important speculation which has since received the title of the nebular hypothesis. In some details, such e.g. as the regarding of the motion of the entire solar system as portion of the general cosmical mechanism, he had predecessors, among others Thomas Wright of Durham, but the work as a whole contains a wonderfully acute anticipation of much that was afterwards carried out by Herschel and Laplace. The hypothesis of the original nebular condition of the system, with the consequent explanation of the great phenomena of planetary formations and movements of the satellites and rings, is unquestionably to be assigned to Kant. (On this question see discussion in W. Hastie's Kant's Cosmogony, as above.)
4. Meditationum quarundam de igne succincta delineatio (1755): an inaugural dissertation, containing little beyond the notion that bodies operate on one another through the medium of a uniformly diffused, elastic and subtle matter (ether) which is the underlying substance of heat and light. Both heat and light are regarded as vibrations of this diffused ether.
5. On the Causes of Earthquakes (1755); Description of the Earthquake of 1755 (1756); Consideration of some Recently Experienced Earthquakes (1756).
6. Explanatory Remarks on the Theory of the Winds (1756). In this brief tract, Kant, apparently in entire ignorance of the explanation given in 1735 by Hadley, points out how the varying velocity of rotation of the successive zones of the earth's surface furnishes a key to the phenomena of periodic winds. His theory is in almost entire agreement with that now received. See the parallel statements from Kant's tract and Dove's essay on the influence of the rotation of the earth on the flow of its atmosphere (1835), given in Zöllner's work, Ueber die Natur der Cometen, pp. 477-482.
7. On the Different Races of Men (1775); Determination of the Notion of a Human Race (1785); Conjectural Beginning of Human History (1786): three tracts containing some points of interest as regards the empirical grounds for Kant's doctrine of teleology. Reference will be made to them in the notice of the Kritik of Judgment.
8. On the Volcanoes in the Moon (1785); On the Influence of the Moon on the Weather (1794). The second of these contains a remarkable discussion of the relation between the centre of the moon's figure and its centre of gravity. From the difference between these Kant is led to conjecture that the climatic conditions of the side of the moon turned from us must be altogether unlike those of the face presented to us. His views have been restated by Hansen.
9. Lectures on Physical Geography (1822): published from notes of Kant's lectures, with the approval of the author.
Consideration of these works is sufficient to show that Kant's mastery of the science of his time was complete and thorough, and that his philosophy is to be dealt with as having throughout a reference to general scientific conceptions. For more detailed treatment of his importance in science, reference may be made to Zöllner's essay on “Kant and his Merits on Natural Science” contained in the work on the Nature of Comets (pp. 426-484); to Dietrich, Kant and Newton, Schultze, Kant and Darwin; Reuschle's careful analysis of the scientific works in the Deutsche Vierteljahrs-Schrift (1868); W. Hastie's introduction to Kant's Cosmogony (1900), which summarizes criticism to that date; and articles in Kant-Studien (1896 foll.).
The notice of the philosophical writings of Kant need not be more than bibliographical, as in the account of his philosophy it will be necessary to consider at some length the successive stages in the development of his thought. Arranged chronologically these works are as follows: —
1755. Principiorum primorum cognitionis metaphysicae novae dilucidatio.
1756. Metaphysicae cum geometria junctae usus in philosophia naturali, cujus specimen I. continet monadologiam physicam.
1762. Die falsche Spitzfindigkeit der vier syltogistischen Figuren, “The False Subtlety of the Four Syllogistic Figures” (trans. T. K. Abbott, Kant's Introduction to Logic and his Essay on the Mistaken Subtilty of the Figures, 1885).
1763. Versuch den Begriff der negativen Grössen in die Weltweisheit einzuführen, “Attempt to introduce the Notion of Negative Quantities into Philosophy.”
1763. Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes, “The only possible Foundation for a Demonstration of the Existence of God.”
1764. Beobachtungen über das Gefühl des Schönen und Erhabenen (Riga, 1771; Konigsberg, 1776).
1764. Untersuchung über die Deutlichkeit der Grundsätze der natürlichen Theologie und Moral, “Essay on the Evidence (Clearness) of the Fundamental Propositions of Natural Theology and Ethics.”
1766. Träume eines Geistersehers, erläutert durch Träume der Metaphysik, “Dreams of a Ghost-seer (or Clairvoyant), explained by the Dreams of Metaphysic” (Eng. trans. E. F. Goerwitz, with introd. by F. Sewall, 1900).
1768. Von dem ersten Grunde des Unterschiedes der Gegenden im Raum, “Foundation for the Distinction of Positions in Space.”
The above may all be regarded as belonging to the precritical period of Kant's development. The following introduce the notions and principles characteristic of the critical philosophy.
1770. De mundi sensibilis et intelligibilis forma et principiis.
1781. Kritik der reinen Vernunft, “Kritik of Pure Reason” (revised ed. 1787; ed. Vaihinger, 1881 foll, and B. Erdmann, 1900; Eng. trans., F. Max Müller, 1896, 2nd ed. 1907, and J. M. D. Meiklejohn, 1854).
1783. Prolegomena zu einer jeden künftigen Metaphysik die als Wissenschaft wird auftreten können, “Prolegomena to all Future Metaphysic which may present itself as Science” (ed. B. Erdmann, 1878; Eng. trans. J. P. Mahaffy and J. H. Bernard, 2nd ed. 1889; Belfort Bax, 1883 and Paul Carus, 1902; and cf. M. Apel, Kommentar zu Kants Prolegomena, 1908).
1784. Idee zu einer allgemeinen Geschichte im weltbürgerlicher Absicht,