p in the
other two.

You do not infer what you can perceive directly by the senses. If Mary
and Kate are standing side by side, you can _see_ which is the taller.
But if they are not side by side, but Mary's height is given as so
much and Kate's as an inch more, then from these two facts you know,
by inference, that Kate is taller than Mary.

"Have we set the table for the right number of people?" "Well, we can
see when the party comes to the table." "Oh! but we can tell now by
counting. How many are there to be seated? One, two, three--fifteen in
all. Now count the places at table--only fourteen. You will have to
make room for one more." This reducing of the problem to numbers and
then seeing how the numbers compare is one very simple and useful kind
of inference.

Indirect comparison may be accomplished by other similar devices. I
can reach around this tree trunk, but not around that, and thus I
perceive that the second tree is thicker than the first, even though
it may not look so. If two things are each found to be equal to a
third thing, then I see they must be equal to each other; if one is
larger than my yardstick and the other smaller, then I see they must
be unequal.

Of the two facts which, taken together, yield an inferred fact, one is
often a general rule or principle, and the inference then consists in
seeing how the general rule applies to a special case. A dealer offers
you a fine-looking diamond ring for five dollars, but you recall the
rule that "all genuine diamonds are expensive", and perceive that this
{467} diamond must be an imitation. This also is an instance of
indirect comparison, the yardstick being the sum of five dollars; this
ring measures five dollars, but any genuine diamond measures more than
five dollars, and therefore a discrepancy is visible between this
diamond and a genuine diamond. You can't see the discrepancy by the
eye, but you see it by way of indirect comparison, just as you
discover the difference between the heights of Mary and Kate by aid of
the yardstick.

If all French writers are clear, then Binet, a French writer, must be
clear. Here "French writers" furnish your yardstick. Perhaps it would
suit this case a little better if, instead of speaking of indirect
comparison by aid of a mental yardstick, we spoke in terms of
"relations". When you have before your mind the relation of A to M,
and also the relation of B to M, you may be able to see, or infer, a
relation be