ABSTRACT
We have all had the experience. Agonizing over a difficult decision—be it a matter of the heart, a moral predicament, a risky financial proposition, or a grave medical decision—we have on occasion wished for ourselves a sage consigliere who would simply tell us the right thing to do. When Joseph Priestley, an eminent 18th-century scientist and discoverer of oxygen, faced a particularly difficult choice, he had no need to dream up a wise man—he knew one. It was Benjamin Franklin, 27 years his senior, one of the Founding Fathers of the United States, and a noted polymath. Asked for his counsel, Franklin did not tell Priestley what to do. Franklin (1772/1987) gave him a potentially even more precious piece of advice—a versatile decision tool that can be employed to decide which of two options to choose, whatever the options may be:
In the Affair of so much Importance to you, wherein you ask my Advice, I cannot for want of sufficient Premises, advise you what to determine, but if you please I will tell you how. … My Way is, to divide half a Sheet of Paper by a Line into two Columns, writing over the one Pro, and over the other Con. Then during three or four Days Consideration I put down under the different Heads short Hints of the different Motives that at different Times occur to me for or against the Measure. When I have thus got them all together in one View, I endeavour to estimate their respective Weights; and where I find two, one on each side, that seem equal, I strike them both out: If I find a Reason pro equal to some two Reasons con, I strike out the three. If I judge some two Reasons con equal to some three Reasons pro, I strike out the five; and thus proceeding I find at length where the Ballance lies; and if after a Day or two of farther Consideration nothing new that is of Importance occurs on either side, I come to a Determination accordingly. And tho’ the Weight of Reasons cannot be taken with the Precision of Algebraic Quantities, yet when each is thus considered separately and comparatively, and the whole lies before me, I think I can judge better, and am less likely to take a rash Step; and in fact I have found great Advantage from this kind of Equation, in what may be called Moral or Prudential Algebra. (p. 878)
