The algebraist before algebra had a name. Diophantus of Alexandria (fl. 3rd century CE) wrote Arithmetica, a problem-solving playground full of clever tricks, unknowns, and proto-equations. His work inspired centuries of number theory — even Fermat couldn’t resist scribbling a note in the margin. Known as “the father of algebra,” he laid the groundwork for symbolic math without ever quite inventing the symbols. Still, he made numbers dance — and that’s what counts.