Praeclarum Theorema/Historical Note

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Historical Note on Praeclarum Theorema

The Praeclarum Theorema was noted and named by Gottfried Wilhelm von Leibniz, who stated and proved it in the following manner:

If $a$ is $b$ and $d$ is $c$, then $ad$ will be $bc$.
This is a fine theorem, which is proved in this way:
$a$ is $b$, therefore $ad$ is $bd$ (by what precedes),
$d$ is $c$, therefore $bd$ is $bc$ (again by what precedes),
$ad$ is $bd$, and $bd$ is $bc$, therefore $ad$ is $bc$.
Q.E.D.


Sources



(Leibniz, Logical Papers, p. 41).
  • 1679 - 1686: Gottfried W Leibniz: Addenda to the Specimen of the Universal Calculus: pp. $40 - 46$