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of mankind, who are thoroughly persuaded that they
reason well enough already. I do not mean to say that they
maintain that none of them ever reasons wrong. Far from that,
though they trust to common sense as affording all the
security that could be desired for reasoning, yet their adhesion
is majestically unanimous to the proposition that of all the race there is but
one single individual who never falls into fallacy; and their only
point of difference is that each is quite sure that he himself is that
man. Unfortunately, to be cocksure that one is an infallible rea-
soner is to furnish conclusive evidence either that one does not
reason at all, or that one reasons very badly, since that deluded
state of mind prevents the constant self-criticism which is, as we
shall see, the very life of reasoning. Congratulations, then, from
my heart go out to you, my dear Reader, whom I assume to have a
sincere desire to learn, not merely the dicta of common sense, but what
good reasoning, scientifically examined, shall prove to be. You are
already an unusually good logician.

But now from what I know of you, I am led to think that
you entertain certain few opinions on which I should like to