Mathematics 

PrinciplesMathematics is a discipline of logic that, starting from assumed but not proved axioms, allows to define a consistent and elegant framework. Complicated? Not really, taking everything into consideration. 
FractalsFractals are not just wonderful images generated by more or less complicated algorithms. They are essential tools to describe physical laws that cannot be represented by "classic" mathematical formulas. 
Duodecimal numbersThe success of decimal system is due only to the fact that at the beginning people used fingers to count. If we could define from scratch a more efficient system, we should use duodecimal numbers. 
Richard Courant e Herbert Robbins, "What is Mathematics? An Elementary Approach to Ideas and Methods.", Oxford University Press, New York, 1941 

Bertrand Russel, "The Principles of Mathematics", Newton Compton, 1983 