A few months back I discussed Benjamin Franklin’s “moral algebra,” his simple prescription for good deliberative decision making.  We know of Franklin’s moral algebra only because he succinctly summarized it in a now-famous short letter to his longtime scientific colleague and friend, Joseph Priestley.  In that letter Franklin seemed to suggest that the moral algebra was his own invention, using phrases such as “My way [of making decisions]…”, but he didn’t explicitly claim it as his own creation.

Recently, one FelixM cryptically commented on this blog that

St Ignatius of Loyola (founder of the Jesuits) recommended this approach, about two hundred years earlier. presumably other people used it before him.

This was intriguing.  What was the method that St Ignatius allegedly used?  Was it indeed the same or very similar to Franklin’s moral algebra? And did Franklin know of it?  Was it indeed the original formulation of the method?

I contacted FelixM, who kindly informed me that St Ignatius’ version of the method could be found in his major work The Spiritual Exercises, which to this day remains a key Jesuit text.   The full text of the relevant section is appended below.

Felix was quite right; Franklin’s moral algebra, and Ignatius’ version, which we might call his “spiritual algebra,” are indeed very similar.

The Ignatius version is however expressed in what appears (to us) archaic and floridly religious language. Here’s my take: a contemporary, secular version of St. Ignatius’ spiritual algebra:

  1. Identify the issue you need to decide upon, framed as whether to take a proposed action or not
  2. Identify and keep in mind  your most important values and objectives.
  3. Cultivate an indifference to the outcome.
  4. List and weigh up the pros and cons of acting in the proposed way, and the pros and cons of not acting.
  5. Determine whether acting has the greater net benefit
  6. Choose what to do based on this determination rather than your gut feeling (“inclination of sense”).

The parallels are striking, but there are some differences:

  1. St Ignatius’ step 2 – identify and keep in mind your most important values and objectives – is not mentioned by Franklin
  2. Franklin recommends listing the pros and cons of taking the action only; he doesn’t recommend also listing the pros and cons of not acting.  [Arguably, these are just the inverse of the pros and cons of acting, and so there is no need to list both.]
  3. Franklin provides a heuristic for determining the balance of considerations (i.e. “cancelling out” considerations of equal weight, etc.) whereas St Ignatius simply instructs us to “reckon” the overall balance.

As to whether Franklin knew of St Ignatius’ method, Felix says:

St Ignatius was pretty well known and I wouldn’t be at all surprised if Franklin had read him.  (In fact, perhaps it would be surprising if he hadn’t!)

This may well be right, but I haven’t been able to find any independent evidence for it.


From The Spiritual Exercises of St. Ignatius of Loyola


It contains six Points.

First Point. The first Point is to put before me the thing on which I
want to make election, such as an office or benefice, either to take or
leave it; or any other thing whatever which falls under an election
that can be changed.

Second Point. Second: It is necessary to keep as aim the end for which
I am created, which is to praise God our Lord and save my soul, and,
this supposed, to find myself indifferent, without any inordinate
propensity; so that I be not more inclined or disposed to take the
thing proposed than to leave it, nor more to leave it than to take it,
but find myself as in the middle of a balance, to follow what I feel to
be more for the glory and praise of God our Lord and the salvation of
my soul.

Third Point. Third: To ask of God our Lord to be pleased to move my
will and put in my soul what I ought to do regarding the thing
proposed, so as to promote more His praise and glory; discussing well
and faithfully with my intellect, and choosing agreeably to His most
holy pleasure and will.

Fourth Point. Fourth: To consider, reckoning up, how many advantages
and utilities follow for me from holding the proposed office or
benefice for only the praise of God our Lord and the salvation of my
soul, and, to consider likewise, on the contrary, the disadvantages and
dangers which there are in having it. Doing the same in the second
part, that is, looking at the advantages and utilities there are in not
having it, and likewise, on the contrary, the disadvantages and dangers
in not having the same.

Fifth Point. Fifth: After I have thus discussed and reckoned up on all
sides about the thing proposed, to look where reason more inclines: and
so, according to the greater inclination of reason, and not according
to any inclination of sense, deliberation should be made on the thing

Sixth Point. Sixth, such election, or deliberation, made, the person
who has made it ought to go with much diligence to prayer before God
our Lord and offer Him such election, that His Divine Majesty may be
pleased to receive and confirm it, if it is to His greater service and