The man who grasps principles can successfully choose his own methods. The man who tries methods, ignoring principles, is sure to have trouble.
--Ralph Waldo Emerson
\begin{bmatrix} 1 & 0 & \ldots & 0 \\
0 & 1 & 0 & \vdots \\
\vdots & 0 & \ddots & 0\\
0 & \ldots & 0 & 1_{n}
\end{bmatrix}