NAND with Equal Arguments/Proof by Truth Table

Proof
We apply the Method of Truth Tables:


 * $\begin{array}{|ccc||cc|} \hline

p & \uparrow & p & \neg & p \\ \hline \F & \T & \F & \T & \F \\ \T & \F & \T & \F & \T \\ \hline \end{array}$

As can be seen by inspection, the truth values under the main connectives match for all boolean interpretations.