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praeclarum theorema (Theorem)

The praeclarum theorema, or splendid theorem, is a theorem of propositional calculus that was noted and named by G.W. 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.
(Leibniz, Logical Papers, p. 41).

Expressed in contemporary logical notation, the praeclarum theorema (PT) may be written as follows:

$\displaystyle ((a \Rightarrow b) \land (d \Rightarrow c)) \Rightarrow ((a \land d) \Rightarrow (b \land c)) $

Representing propositions as logical graphs under the existential interpretation, the praeclarum theorema is expressed by means of the following formal equation:

\includegraphics[scale=0.8]{PraeclarumTheoremaFigure1} (1)

And here's a neat proof of that nice theorem.

\includegraphics[scale=0.8]{PraeclarumTheoremaFigure2} (2)

References

  • Leibniz, Gottfried W. (1679-1686 ?), “Addenda to the Specimen of the Universal Calculus", pp. 40-46 in G.H.R. Parkinson (ed., trans., 1966), Leibniz : Logical Papers, Oxford University Press, London, UK.

Readings

  • Sowa, John F. (2002), “Peirce's Rules of Inference", Online.

Resources



"praeclarum theorema" is owned by Jon Awbrey.
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Other names:  splendid theorem
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Cross-references: proof, equation, propositional calculus, theorem
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This is version 10 of praeclarum theorema, born on 2008-02-10, modified 2008-10-21.
Object id is 10255, canonical name is PraeclarumTheorema.
Accessed 699 times total.

Classification:
AMS MSC01A45 (History and biography :: History of mathematics and mathematicians :: 17th century)
 03-03 (Mathematical logic and foundations :: Historical )
 03B05 (Mathematical logic and foundations :: General logic :: Classical propositional logic)
 03B22 (Mathematical logic and foundations :: General logic :: Abstract deductive systems)
 03B35 (Mathematical logic and foundations :: General logic :: Mechanization of proofs and logical operations)
 03B70 (Mathematical logic and foundations :: General logic :: Logic in computer science)

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