The Forty-Seventh Problem of Euclid
The Pythagorean theorem, taught as an emblem that a Mason should be a general lover of the arts and sciences.
Also called: 47th problem of Euclid · 47th proposition · Pythagorean theorem
What it means
Proposition 47 of Book I of Euclid's Elements: in a right triangle the square on the hypotenuse equals the sum of the squares on the other two sides. Webb lists it among the Master Mason's emblems and attributes it, as the tradition does, to Pythagoras.
Its practical use to a builder is real: a 3-4-5 triangle gives you a true right angle with nothing but a cord, which is how you make a square in the first place.
In England and in jurisdictions following English practice, the diagram hangs inside the square as the Past Master's jewel. American Past Masters' jewels usually use the compasses and quadrant instead; see the Past Master's jewel.
Related Lodge offices: Past Master
Frequently asked questions
What does the Forty-Seventh Problem of Euclid mean in Freemasonry?
The Pythagorean theorem, taught as an emblem that a Mason should be a general lover of the arts and sciences.
Who can wear the Forty-Seventh Problem of Euclid?
This is a lesson rather than a badge. It turns up on Lodge charts, prints and gifts, and owning or displaying one says nothing about rank. On a lapel most people will read it as Masonic.
Sources
Drawn from the published monitors and from what the bodies concerned publish about themselves. Nothing here comes from, or goes beyond, any obligated material.
- Thomas Smith Webb, The Freemason's Monitor; or, Illustrations of Masonry (1797)
- Albert G. Mackey, An Encyclopædia of Freemasonry (1873)
- Euclid, Elements, Book I, Proposition 47