Remembering Abraham Lincoln

Today -- April 14, 2015 -- marks the 150th birthday of the assassination of President Abraham Lincoln (1809 - 1865) and April 15 is the date on which he died. Lincoln loved poetry and trained his reasoning with Euclid's geometry.  Here is a brief sample of his own poetry (found -- along with other samples -- at PoetryFoundation.org).

       Abraham Lincoln     by Abraham Lincoln

       Abraham Lincoln
       his hand and pen
       he will be good but
       god knows When

From my copy of Walt Whitman's Leaves of Grass (Signet Classics, 1955), from the section "Memories of Lincoln," I have copied these well-known and thoughtful (and non-mathematical) lines:

Lincoln and Euclid -- common notions

     This afternoon I enjoyed the recently-released film, Lincoln -- appreciating Sally Fields as Mary Todd, Tommy Lee Jones as Thaddeus Stevens and (especially) Daniel Day-Lewis as Abraham Lincoln. An absorbing drama -- inspiring and also informative.  With a slight mention of mathematics:  in a film conversation with two-young telegraph operators, Lincoln reflected on his study of Euclid and shared with the young men the first of Euclid's common notions:

     Things that are equal to the same thing are equal to each other.