“Conscience is but a word that cowards use,

Devised at first to keep the strong in awe:

Our strong arms be our conscience, swords our law.

March on, join bravely, let us to’t pell-mell

If not to heaven, then hand in hand to hell.”

—William Shakespeare, Richard III, Act 5, Scene 3, lines 336-440.

Sources:

http://www.bartleby.com/70/3353.html

http://shakespeare.mit.edu/richardiii/richardiii.5.3.html

http://absoluteshakespeare.com/plays/richard_III/a5s3.htm