2300 years ago Euclid proclaimed as one of his common
notions that things equal to the same thing are also equal to each other. This
is a founding principle of geometry and necessary for the beginnings of modern
engineering. It seems self-evident, doesn’t it? Of course Thomas Jefferson held
it self-evident that all men are created equal and endowed with unalienable
rights such as liberty, yet he was himself a slave owner. In Steven Spielberg’s
masterful biopic Lincoln, the 16th
President and drafter of the Emancipation Proclamation tries to rely on
Euclid’s notion to help him in his decisions regarding slavery that will impact
the United States and the terrible Civil War that was entering its fifth bloody
year.
