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Benjamin Franklin on Decision Analysis
Is this the origin of Multi Criteria Decision Analysis in Benjamin
Franklins letter to Dr Priestly?
London, Sept. 19. 1772
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 of 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 Balance 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 make 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.
Thanks to our friends at the Ministry of Defence for bringing this
excellent letter to our attention.
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