PORTLAND – When I was a boy in the early 1950s, my parents gave me a book on Abraham Lincoln. It was a picture book, a compilation of all the known photographs of our great president.

Captivated as I was with the vivid illustrations that abounded from cover to cover, the book’s most memorable part would prove to be a few words found in its introduction. Here the author, Stefan Lorant, explained his book’s genesis.

Lorant, a German journalist in the 1920s and an opponent of Adolf Hitler, had been quickly thrown into a concentration camp in 1933 when Hitler came to power. It was thus behind prison walls, Lorant explained in his introduction, that “I made my acquaintance with Abraham Lincoln” when “I happened to pick an old volume containing (his) speeches” from a laundry basket full of books being passed from cell to cell.

“A prison cell,” Lorant continued, “is just the right place to get the impact of Lincoln’s philosophy and be lured under his spell.”

These words struck me. That stark, contrasting image between Hitler’s cell and Lincoln’s words would ever linger in my mind, a disjunction providing both an impetus and a framework for a lifelong study of each man’s life and political philosophy.

In my quest for Lincoln I obtained a book on the famous 1858 Lincoln-Douglas debates. What stood out following the debates, during which he campaigned for Stephen Douglas’ Senate seat, was Lincoln’s consistent reliance on fact and logic as he debated our great issue of the day: slavery.

“Reason, cold, calculating, unimpassioned reason,” Lincoln had urged as a political guide 20 years earlier, and now reason provided the underpinning for his appeal to his fellow citizens.

Not so Hitler. As I waded into “Mein Kampf,” Hitler’s 1925 autobiography, it became readily clear that for him facts were not relevant and that his appeal to his fellow Germans was not to reason. Propaganda, this aspirant to political office wrote, must be aimed not at the intellect but at the emotions of the citizenry.

From this fundamental divide in their political philosophies, much would follow during their respective lifetimes.

With the onset of the Great Depression in 1929, plunging German democracy into the depths of political crisis, Hitler campaigned with a deluge of lies and a relentless appeal to the emotions — to fear, to anger, to hatred, to the worst that he could tap within his fellow citizens. Once in power, he proved to be the ultimate extremist and consummate ideologue.

Lincoln was no ideologue. While he ran for president amidst the emotion, irrationality and extremism that presaged our nation’s most severe political crisis, reason remained his guide. As the late professor David Donald has illustrated, Lincoln’s political philosophy was consistent with “the fundamental pragmatic element in the American political tradition.”

Elected president, Lincoln countered the extremism of both North and South with moderation. From his first inaugural, summoning “the better angels of our nature” to his second inaugural, delivering (with an assassin’s bullet a month away) his immortal words “with malice toward none, with charity for all,” Lincoln consistently sought the best within us.

Hitler, as Fuhrer, was guided by his emotions. Holding to his ideology and wallowing in the irrational, he led his country down a path to destruction and humanity to unimaginable horrors.

Lincoln, as president, let reason be his guide. His politically pragmatic path saved our democracy and ended the scourge of slavery.

As Stefan Lorant’s captivity exemplified, Lincoln and Hitler stand as opposing beacons — two polar opposite beacons that shall stand as guides for the ages. Here, early in my life, were navigational aids to a resolve in matters political: Ever avoid extremism and appeals to the emotions, ever steer toward moderation and reason.

Parker B. Albee Jr. is a professor of history at the University of Southern Maine in Portland.