[G09] Decision by pros and cons


One very practically useful method of making decisions is to use a pros and cons list. "Pros" are the good reasons or good consequences that are in favor of the decision. "Cons" are the opposite, i.e. the disadvantages or bad points about the decision.

When you have to decide whether to carry out a course of action, get a piece of paper and write down in two columns the pros and cons of the decision. Try to be comprehensive so you will end up with a clear picture of what is at stake. The general idea is that if there are more pros than cons, then you go ahead and carry out the proposed action. If there are more cons than pros, then you refrain from doing it. If it is a tie, then you can proceed either way.

Benjamin Franklin was a very famous American politician, scientist, and author. He invented the lightning rod, bifocal lens, used a kite to conduct electricity from clouds, helped set up the University of Pennsylvania, contributed to the US Declaration of Independence, and accomplished lots of other things. You would expect that such a amazing person must have been very good at making decisions. The British scientist Joseph Priestley, who discovered oxygen, actually asked Franklin for advice about making decisions, and Franklin wrote this letter in replying providing the first ever description of the pros and cons method:

To Joseph Priestley
London, September 19, 1772

Dear Sir,

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.

When these difficult Cases occur, they are difficult chiefly because while we have them under Consideration all the Reasons pro and con are not present to the Mind at the same time; but sometimes one Set present themselves, and at other times another, the first being out of Sight. Hence the various Purposes or Inclinations that alternately prevail, and the Uncertainty that perplexes us.

To get over this, 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.

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

Yours most affectionately

B. Franklin

Source: Mr. Franklin: A Selection from His Personal Letters. Contributors: Whitfield J. Bell Jr., editor, Franklin, author, Leonard W. Labaree, editor. Publisher: Yale University Press: New Haven, CT 1956.

There are a few noteworthy points in this letter:

  1. The whole exercise is carried out within a few days. Of course, sometimes we need to decide quickly. But often it is useful to spend more time thinking carefully about a difficult and important decision. It gives our mind a better understanding of the situation, and helps us come up with a more comprehensive list of pros and cons. In addition, this avoids acting impulsively in a rush.
  2. Franklin realized that some reasons are more weightly than others and this should be taken into account. Just because an action has 5 pros and 3 cons does not mean that we must go ahead. Perhaps some of the cons are very serious. This should be taken into account.
  3. Franklin also admitted that this is not a precise mathmatical method. But having every relevant consideration in front of us can be very helpful nonetheless. It might also be a good idea to keep the pieces of paper that we used to make such decisions. We can then review our track record periodically to see if we are prone to biases and can try to correct our mistakes and do better in the future.
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