ll calamities. We call in the doctor to save us from death; and,
death being admittedly an evil, he has the right to administer the
queerest and most recondite pill which he may think is a cure for all
such menaces of death. He has not the right to administer death, as
the cure for all human ills. And as he has no moral authority to
enforce a new conception of happiness, so he has no moral authority
to enforce a new conception of sanity. He may know I am going mad; for
madness is an isolated thing like leprosy; and I know nothing about
leprosy. But if he merely thinks my mind is weak, I may happen to
think the same of his. I often do.

In short, unless pilots are to be permitted to ram ships on to the
rocks and then say that heaven is the only true harbour; unless judges
are to be allowed to let murderers loose, and explain afterwards that
the murder had done good on the whole; unless soldiers are to be
allowed to lose battles and then point out that true glory is to be
found in the valley of humiliation; unless cashiers are to rob a bank
in order to give it an advertisement; or dentists to torture people to
give them a contrast to their comforts; unless we are prepared to let
loose all these private fancies against the public and accepted
meaning of life or safety or prosperity or pleasure--then it is as
plain as Punch's nose that no scientific man must be allowed to meddle
with the public definition of madness. We call him in to tell us where
it is or when it is. We could not do so, if we had not ourselves
settled what it is.

As I wish to confine myself in this chapter to the primary point of
the plain existence of sanity and insanity, I will not be led along
any of the attractive paths that open here. I shall endeavour to deal
with them in the next chapter. Here I confine myself to a sort of
summary. Suppose a man's throat has been cut, quite swiftly and
suddenly, with a table knife, at a small table where we sit. The
whole of civil law rests on the supposition that we are witnesses;
that we saw it; and if we do not know about it, who does? Now suppose
all the witnesses fall into a quarrel about degrees of eyesight.
Suppose one says he had brought his reading-glasses instead of his
usual glasses; and therefore did not see the man fall across the table
and cover it with blood. Suppose another says he could not be certain
it was blood, because a slight colour-blindness was hereditary in his
family. Suppose a third s