Complete the famous Pythagoras quote "All things are…"?

Didn't understand it at school and in my 60's, still don't!!

I believe the answer given. But it seems strange, the ancient Greeks thought of geometry as the "normal" maths, numbers weren't used much, and algebra less so. The Pythagorean theorem of right triangles was given geometrically. It is a modern view to us a^2 + b^2 = c^2