Everything existing in the Universe is the fruit of chance and necessity.
Nothing is so easy as to deceive one's self; for what we wish, that we readily believe.
Nothing exists except atoms and empty space; everything else is opinion.
I am the most travelled of all my contemporaries; I have extended my field of enquiry wider than anyone else; I have seen more countries and climes and have heard more speeches of learned men. No one has surpasssed me in the composition of lines according to demonstration, not even the Egyptian knotters of ropes or geometers.
Quoted in A L Mackay, Dictionary of Scientific Quotations (London 1994)