Complete liberty of contradicting and disproving our opinion, is the very condition which justifies us in assuming its truth for purposes of action.
John Stuart MillEvery opinion which embodies somewhat of the portion of truth which the common opinion omits, ought to be considered precious, with whatever amount of error and confusion that truth may be blended.
John Stuart MillThe peculiarity of the evidence of mathematical truths is that all the argument is on one side.
John Stuart Mill