5. But, writes J. S. Mill, _On Liberty_, "we can never be sure that the opinion we are endeavouring to stifle is a false opinion." If we cannot, then is there no such thing as certainty upon any point of morals, politics, or religion. Assassination of tyrants, whether in public or private life, may be wickedness, or it may be a laudable outburst of public spirit, who knows? Which of us is sure that all property is not theft? Plato's views on marriage and infanticide may be correct: the Nihilist may be your true politician; and all our religious knowledge dwindles down to the confession of Protagoras: "Concerning Gods, I find no clear evidence whether they are or are not, or what manner of beings they are." These are the sceptical tremors which this denial induces. But even scepticism has its proof, which Mill furnishes as follows: "All silencing of discussion is an assumption of infallibility." The very name _infallibility_ has an effect upon the modern Englishman like that of _Popery_ upon his forefathers. It shakes his nerves, obscures his judgment, and scares his seated reason to leap up from her throne. But after we have recovered from our fright, we recollect that, whereas infallibility is an all-round attribute, compassing an entire subject, certainty goes out to one particular point on the circumference; we may then be certain without being infallible. Extremely fallible as I am in geography, I am nevertheless certain that Tunis is in Africa. Silencing discussion is an assumption, not of infallibility, but of certainty. The man who never dares assume that he is certain of anything, so certain as to close his ears to all further discussion, comes nothing short of a universal sceptic.