1. 10

    Your assumptions are your windows on the world. Scrub them off every once in a while, or the light won't come in.

  2. 9

    We now have a whole culture based on the assumption that people know nothing and so anything can be said to them.

  3. 8

    You must stick to your conviction, but be ready to abandon your assumptions.

  4. 7

    When speculation has done its worst, two and two still make four.

  5. 6

    The temptation to form premature theories upon insufficient data is the bane of our profession.

  6. 5

    Theories are always very thin and insubstantial, experience only is tangible.

  7. 4

    A speculator is a man who observes the future, and acts before it occurs.

  8. 3

    It is theory that decides what can be observed.

  9. 2

    There are two times in a man's life when he should not speculate: when he can't afford it, and when he can.

  10. 1

    One must credit an hypothesis with all that has had to be discovered in order to demolish it.