Euclid's manner of exposition, progressing relentlessly from the data to the unknown and from the hypothesis to the conclusion, is perfect for checking the argument in detail but far from being perfect for making understandable the main line of the argument. George Pólya
The right way to ask the question is: How does the concept of a point fit into the logical structure of Euclid's geometry? ...It cannot be answered by a definition. Freeman Dyson
Euclid's postulates came from the Pythagorean theorem, not the other way around. Richard Hamming
According to Pappus, "Apollonius, having completed Euclid's four books of conics and added four others, handed down eight volumes of conics." Source: Internet
A large body of mathematical work would still be valid when calling 1 a prime, but Euclid's fundamental theorem of arithmetic (mentioned above) would not hold as stated. Source: Internet
Although Schopenhauer could see no justification for trying to prove Euclid's parallel postulate, he did see a reason for examining another of Euclid's axioms. Source: Internet