It is through wonder that men now begin and originally began to philosophize; wondering in the first place at obvious perplexities, and then by gradual progression raising questions about the greater matters too.

-Aristotle
Metaphysics, bk.1, ch.2, 982 (translated by H  Tredennick).

Without contraries is no progression. Attraction and repulsion, reason and energy, love and hate, are necessary to human existence.

-Blake,William
  The Marriage of Heaven and Hell,'The Argument'.

The entirehistoryof scienceisa progressionofexploded fallacies, not of achievements. 678

-Rand, Ayn
  Atlas Shrugged.