I'm not sure exactly when I was introduced to the concepts behind Sir Isaac Newton's laws of motion.  While behavioral finance has laid claim to the concept of (and means of combatting) inertia in benefit plan design, Newton's first law of motion (sometimes called "the law of inertia") — first published in the late 1600s — reminds us that (in layman's terms), an object at rest remains at rest; or perhaps more precisely, an object continues to do whatever it happens to be doing unless a force is exerted upon it. 

However, the one I remember most from earlier days is the third law of motion — the notion that for every action there is an equal and opposite reaction. To this day, I have a "Newton's cradle" at my desk.

While Newton's laws were intended to explain the motion of objects, they do seem to have application in matters of human interaction as well. One need only look at the increasingly strident levels of partisanship on Capitol Hill to appreciate the stridency of "equal and opposite" reactions.