There Are No Solved Problems;

What Is A Good Definition? For The Philosopher Or The Scientist, It Is A Definition Which Applies To All The Objects To Be Defined, And Applies Only To Them; It Is That Which Satisfies The Rules Of Logic. But In Education It Is Not That; It Is One That Can Be Understood By The Pupils.

A Small Error In The Former Will Produce An Enormous Error In The Latter.

It May Happen That Small Differences In The Initial Conditions Produce Very Great Ones In The Final Phenomena.

Zero Is The Number Of Objects That Satisfy A Condition That Is Never Satisfied. But As Never Means "in No Case", I Do Not See That Any Progress Has Been Made.

Logic Sometimes Makes Monsters. For Half A Century We Have Seen A Mass Of Bizarre Functions Which Appear To Be Forced To Resemble As Little As Possible Honest Functions Which Serve Some Purpose.