Sales Compendium

What follows is a copy of a letter written by Benjamin Franklin to Joseph Priestly [the man usually credited with the discovery of oxygen]. Priestly was trying to decide whether to accept a new position or not and had sought Franklin’s advice. The letter is dated 19th September 1772.

In affairs of such importance to you, wherein you ask my advice, I cannot, for want of sufficient premises, counsel you what to determine; but, if you please, I will tell you how.

When these difficult cases occur, they are difficult chiefly because while we have them under consideration, all the reasons – pros and cons – are not present to the mind at the same time. Hence the various purposes or inclinations that alternatively prevail, and the uncertainty that perplexes us.

To get this over, my way is to 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 got these 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’ equals 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 balance lies; and if, after a day or two of further consideration, nothing new that is of importance occurs on either side, I come to a determination accordingly.

And, although the weight of reasons cannot be taken with 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 liable to make a rash step; in fact, I have found great advantage from this kind of equation in what may be called moral or prudential algebra.

Wishing sincerely that you may determine for the best, I am ever, my dear friend,

Yours most affectionately,

Benjamin Franklin

Note: While there are many places where this letter can be found, this version comes from ‘Benjamin Franklin and Prudential Algebra’, an article by W L Etter in Decision Sciences published in 1974, Volume 5(1).