I’ve seen a number of claims that historical figures were Freemasons based on the presence of “Masonic symbols” in portraits of them. For instance. The Flat Earther Eric Dubay claims that “From Pythagoras to Copernicus, Galileo and Newton, to modern astronauts like Aldrin, Armstrong and Collins, to director of NASA and Grand Commander of the 33rd degree C. Fred Kleinknecht, the founding fathers of the spinning ball mythos have all been Freemasons! “ The text version of this claim is at http://www.atlanteanconspiracy.com/2015/08/200-proofs-earth-is-not-spinning-ball.html, He makes the same claim in his YouTube video at . At around 108 minutes, but the text version is easier to access. In both case it's his point 191. I having made a lot of replies in comments, on YouTube and later collected my own point-by point replies at http://roundearthsense.blogspot.co.uk/. You can guess how much the flat earthers have engaged in debate, though. He supports this with this graphic. https://www.metabunk.org/data/MetaMirrorCache/afe1e175561c5e1d30190c8075ebaccc.jpg And this one https://www.metabunk.org/data/MetaMirrorCache/ef11bdd37b9cdd33b9476dce4b387065.jpg I'll leave aside the different hand positions, as too weak to be worth debunking. (Edit) I see the hand sign claim has already been debunked. https://www.metabunk.org/can-someone-please-debunk-the-masonic-hidden-hand-sign.t1278/#post-32012 The only evidence he offers that all these thinkers were Freemasons is the presence of a pair of compasses, or sometimes a square, in portraits of them. Now, it's certainly true that Freemasons use the square and compasses as a symbol. That's because actual masons, that is builders in stone, have used these for many centuries as tools in their work. So did anyone whose work involved measuring and drawing accurately. In fact, that is the meaning of the compasses or setsquare in these pictures: they denote precision and care in measurement. It's a little like the way that many present-day portraits of thinkers include a computer in the picture. These are standard tools used by builders, architects, map-makers, artists, architects, navigators and many others. Often, they have been used as symbols of those trades, too. By pure chance, I noticed an example of this while I was thinking about Dubay's claim. I am a volunteer steward in a local museum, and I noticed this map on the wall there. Here again is the symbol of the compasses marking out the scale on the map, and implying accurate and careful measurement. There's clearly no necessary connection with the Freemasons when you see that. Later, I noticed these compasses in a display of coopers’ tool for making barrels. Does this imply that barrel makers were freemasons? No, they just needed to measure precisely so that their barrels didn't leak. And, while I was tidying up the map photo above to post it, I noticed the icon for the tool I used to crop out the surrounding wall: Yes, it's the square from the square and compasses, as seen beside Pythagoras, Copernicus and Galileo in Dubay's "evidence". Does this mean that this standard symbol in my image editor program is a secret tool of the Freemasons? No, it means that it depicts the tool traditionally used to get right-angles straight. As it does in Dubay's pictures. Edit: Trailblazer suggests below that this is actually a photographic matte. That's probably true, though I suspect that the shape of the matte was derived from the old square tool. As he says, the point remains valid; it's a functional tool shape not a symbol of freemasonry. By the way, is Dubay really claiming that Freemasonry existed more than 2500 years ago, at the time of Pythagoras?