Gottfried Wilhelm Leibniz, Philosophical Essays, tr. Roger Ariew and Daniel
Garber (Indianapolis: Hackett Publishing Company, 1989), p. 123.
Ernan McMullin, Newton on Matter and Activity (Notre Dame: University of
Notre Dame Press, 1978), p. 32. I rely heavily on his account of the differences
and similarities between Descartes, Leibniz, and Newton.
McMullin, Newton on Matter and Activity, p. 33. It should, however, be remem¬
bered that force was for Newton not essential to matter.
Ak 1, p. 17.
Ak 1, p. 139.
Ibid, (the phrase represents the subtitle of Part III). This contrast between math¬
ematical body and body of nature can be found in Christian August Crusius, who
had argued that the space that substances fill is not the same as mathematical
space, that mathematical space is arbitrary, and that it can therefore not be ap¬
plied to nature without problems. See Entwurf der notwendigen Vernunftwahr¬
heiten, wiefern sie den zufälligen entgegengesetzt werden (1745), now in Christian
August Crusius, Die philosophischen Hauptwerke, ed. G. Tonelli (Hildesheim: Olms,
1964); see especially p. 175. Compare Reinhard Finster, "Zur Kritik von Chris¬
tian August Crusius an den einfachen Substanzen bei Leibniz und Wolff," Stu-
dia Leibnitiana 18 (1986), pp. 72—82. However, it is more likely that Kant relies
on Alexander Gottlieb Baumgarten's Metaphysica, which first appeared in 1739,
and which inspired both Crusius and Kant. Baumgarten made a distinction be¬
tween fictional or mathematical points and monads, which are real and determinate
physical points. But whether or not Baumgarten influenced Crusius, his con¬
ception of physical monads certainly represents almost exactly Kant's own early
view. See especially paragraphs 392-435 (Ak 17, pp. 109-117).
Ak 1, p. 140.
Ak 1, pp. 15if. Kant's theory must also be viewed in relation to the question that
the Berlin Academy had formulated for the year 1747 (published in 1746): "We
demand an examination, starting from an exact and clear presentation of the doc¬
trine of monads, whether monads can be thoroughly disproved and destroyed by
incontestable arguments, or whether it is possible to prove the monads and de¬
rive from them an intelligible explanation of the main phenomena of the universe
and especially of the origin and the motion of bodies" (emphasis supplied). For an
account of the discussion connected to this question, see KarlVogel, Kant und die
Paradoxien der Vielheit. Die Monadenlehre in Kants philosophischer Entwicklung bis
zum Antinomienkapitel der Kritik der reinen Vernunft (Meisenheim am Glan: Anton
Hain, 1975), pp. 87f.
At Ak 1, p. 152. Kant refers to this work.
McMullin, Newton on Matter and Activity, p. 46.
Baumgarten, Metaphysica, paragraphs 294 (Ak 17, p. 91) and 210-223 (Ak 17,
pp. 70-76), especially 220 (p. 74). But compare also Erdmann, Knutzen, pp. 95-
Erdmann claims that Baumgarten's preestablished harmony was different
from Leibniz's because Baumgarten held that monads can act on each other. This
is certainly true, but this does not mean that his theory was one of physical in¬
flux. Just like Kant, Baumgarten believes that external influences (what he calls
