Wie manches wu« rde in derTheorie unwidersprechlich scheinen, wenn es dem Genie nicht gelungen w a« re, das Widerspiel durch dieTat zu erweisen. How many things would have appeared incontestable in theory if genius had not proved them wrong in practice. Levant
Rien n'est plus incontestable que l'existence de nos sensations; ...jean le rond d'alembert
It is essential to grasp the incontestable truth that a Marxist must take cognisance of real life, of the true facts of reality , and not cling to a theory of yesterday, which, like all theories, at best only outlines the main and the general, only comes near to embracing life in all its complexity.
Cautiousness in judgment is nowadays to be recommended to each and every one: if we gained only one incontestable truth every ten years from each of our philosophical writers the harvest we reaped would be sufficient. ... To grow wiser means to learn to know better and better the faults to which this instrument with which we feel and judge can be subject.Georg Christoph Lichtenberg