“Don’t be so sure—nobody can be certain of anything.” Bertrand Russell’s
gibberish to the contrary notwithstanding, that pronouncement includes itself;
therefore, one cannot be sure that one cannot be sure of anything. The
pronouncement means that no knowledge of any kind is possible to man, i.e.,
that man is not conscious. Furthermore, if one tried to accept that catch
phrase, one would find that its second part contradicts its first: if nobody
can be certain of anything, then everybody can be certain of everything he
pleases—since it cannot be refuted, and he can claim he is not certain he is
certain (which is the purpose of that notion).