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Viewing Version 8 of 'praeclarum theorema'
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Title of object: praeclarum theorema
Canonical Name: PraeclarumTheorema
Type: Theorem

Created on: 2008-02-10 14:51:27
Modified on: 2008-09-02 15:05:13

Creator: Jon Awbrey
Modifier: Jon Awbrey
Author: Jon Awbrey

Classification: msc:01A45, msc:03-03, msc:03B05, msc:03B22, msc:03B35, msc:03B70
Synonyms: praeclarum theorema=splendid theorem

Preamble:

% this is the default PlanetMath preamble. as your knowledge
% of TeX increases, you will probably want to edit this, but
% it should be fine as is for beginners.

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\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{graphicx}

% used for TeXing text within eps files
%\usepackage{psfrag}
% need this for including graphics (\includegraphics)
%\usepackage{graphicx}
% for neatly defining theorems and propositions
%\usepackage{amsthm}
% making logically defined graphics
%\usepackage{xypic}

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% define commands here
Content:

\PMlinkescapeword{ad}
\PMlinkescapeword{AD}
\PMlinkescapeword{c}
\PMlinkescapeword{C}
\PMlinkescapeword{calculus}
\PMlinkescapeword{Calculus}
\PMlinkescapeword{qed}
\PMlinkescapeword{QED}
\PMlinkescapeword{reflect}
\PMlinkescapeword{Reflect}

The \textbf{praeclarum theorema}, or \textit{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:

\begin{quote}
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, \textit{Logical Papers}, p. 41).
\end{quote}

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

\[ ((a \Rightarrow b) \land (d \Rightarrow c)) \Rightarrow ((a \land d) \Rightarrow (b \land c)) \]

Under the existential interpretation of logical graphs, the praeclarum theorema is represented by means of the following formal equivalence or logical equation.

\begin{center}\begin{tabular}{cc}
\includegraphics[scale=0.8]{PraeclarumTheoremaFigure1} & (1) \\
\end{tabular}\end{center}

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

\begin{center}\begin{tabular}{cc}
\includegraphics[scale=0.8]{PraeclarumTheoremaFigure2} & (2) \\
\end{tabular}\end{center}

\section{References}
\begin{itemize}
\item
Leibniz, Gottfried W. (1679--1686 ?), ``Addenda to the Specimen of the Universal Calculus", pp. 40--46 in G.H.R. Parkinson (ed., trans., 1966), \textit{Leibniz : Logical Papers}, Oxford University Press, London, UK.
\end{itemize}

\section{Readings}
\begin{itemize}
\item
Sowa, John F. (2002), ``Peirce's Rules of Inference", \PMlinkexternal{Online}{http://www.jfsowa.com/peirce/infrules.htm}.
\end{itemize}

\section{Resources}
\begin{itemize}
\item
Megill, Norman (2008), \PMlinkexternal{Praeclarum Theorema}{http://us.metamath.org/mpegif/prth.html} @ \PMlinkexternal{Metamath Proof Explorer}{http://us.metamath.org/mpegif/mmset.html}.
\end{itemize}