One philosopher used this principle to refute the existence of absolute space, since if absolute space existed, there would be no reason why east and west could not be swapped. For 10 points each:
[10m] Name this principle which, along with the principle of non-contradiction, grounds all truths according to the Monadology. Arthur Schopenhauer adapted his PhD thesis into a book “On the Fourfold Root” of this principle.
ANSWER: principle of sufficient reason [or Satzes vom zureichenden Grunde; accept On the Fourfold Root of the Principle of Sufficient Reason or Ueber die vierfache Wurzel des Satzes vom zureichenden Grunde]
[10e] The principles of non-contradiction and sufficient reason are formulated in the Monadology, a work by this German rationalist philosopher who independently developed calculus.
ANSWER: Gottfried Wilhelm von Leibniz
[10h] In the Monadology, Leibniz argues that there must be sufficient reason for statements with this property, since otherwise only an infinite process of resolution could demonstrate them to be identities.
ANSWER: contingent [or contingency; accept truths of fact]