Zeno of Sidon could be well described as a non-conformist or a very critical mathematician. Born in approximately 150 B.C, in Sidon or presently Saida in Lebanon,  Zeno was particularly critical of Euclid's work with Geometry.  Specifically, Zeno criticized Euclid's 1st proposition on the grounds that it was necessary for Euclid to include an axiom stating that two straight lines can intersect in at most one point.  Furthermore, Zeno was also reluctant to accept the existence of a right angle.  He challenged Euclid's proof on the equality of right triangles. For this reason, Zeno could be considered the pioneer of non-Euclidean geometry.

Author: Filiberto Barajas

References:
Biography in Dictionary of Scientific Biography (New York, 1970-1990)

G Vlastos, Zeno of Sidon as a Critic of Euclid.  The Classical Tradition:  Literary and Historical Studies in Honor of Harry Caplan  (New York, 1966), 148-159. As listed in URL
http://www-history.mcs.st-andrews.ac.uk/history/Mathematicians/Zeno_of _Sidon.html