those that you have already
tried.

Nothing can be more simple than that, you think; but if you will take
the trouble to analyse and trace out into its logical elements what has
been done by the mind, you will be greatly surprised. In the first place
you have performed the operation of induction. You found that, in
two experiences, hardness and greenness in apples went together with
sourness. It was so in the first case, and it was confirmed by the
second. True, it is a very small basis, but still it is enough to make
an induction from; you generalise the facts, and you expect to find
sourness in apples where you get hardness and greenness. You found upon
that a general law that all hard and green apples are sour; and that,
so far as it goes, is a perfect induction. Well, having got your natural
law in this way, when you are offered another apple which you find is
hard and green, you say, "All hard and green apples are sour; this
apple is hard and green, therefore this apple is sour." That train of
reasoning is what logicians call a syllogism, and has all its various
parts and terms,--its major premiss, its minor premiss and its
conclusion. And, by the help of further reasoning, which, if drawn out,
would have to be exhibited in two or three other syllogisms, you arrive
at your final determination, "I will not have that apple." So that, you
see, you have, in the first place, established a law by induction, and
upon that you have founded a deduction, and reasoned out the special
particular case. Well now, suppose, having got your conclusion of the
law, that at some time afterwards, you are discussing the qualities
of apples with a friend: you will say to him, "It is a very curious
thing,--but I find that all hard and green apples are sour!" Your friend
says to you, "But how do you know that?" You at once reply, "Oh, because
I have tried them over and over again, and have always found them to be
so." Well, if we were talking science instead of common sense, we should
call that an experimental verification. And, if still opposed, you go
further, and say, "I have heard from the people in Somersetshire and
Devonshire, where a large number of apples are grown, that they have
observed the same thing. It is also found to be the case in Normandy,
and in North America. In short, I find it to be the universal experience
of mankind wherever attention has been directed to the subject."
Whereupon, your friend, unless he is a very unr