Economics as a positive science is a body of tentatively accepted generalizations about economic phenomena thatcanbe used topredicttheconsequences ofchanges in circumstances.

-Friedman, Milton
  'The Methodology of Positive Economics' in Essays in Positive Economics.

Science proceeds by successive answers to questions more and more subtle, coming nearer and nearer to the very essence of phenomena.

-Pasteur, Louis
c.1856  EŁ  tudes sur la bie'  re, ch.6 (translated by Rene¤   Dubois).