UnScramble this Word: r m p s e l t a?

Questions

Who said 'Everything must either be or not be, whether in the present or in the future'?

Who said 'Give me a firm place to stand and I will move the Earth'?

Who said 'So far as the laws of mathematics refer to reality they are not certain. And so far as they are certain, they do not refer to reality.'?

Who said 'The greater our knowledge increases, the more our ignorance unfolds'?

Who said 'The way of the warrior is the resolute acceptance of death'?