--the great and
principal act of ratiocination in man, as logicians tell us, is the
finding out the agreement or disagreement of two ideas one with another,
by the intervention of a third (called the medius terminus); just as a
man, as Locke well observes, by a yard, finds two mens nine-pin-alleys
to be of the same length, which could not be brought together, to
measure their equality, by juxta-position.

Had the same great reasoner looked on, as my father illustrated his
systems of noses, and observed my uncle Toby's deportment--what great
attention he gave to every word--and as oft as he took his pipe from
his mouth, with what wonderful seriousness he contemplated the length of
it--surveying it transversely as he held it betwixt his finger and
his thumb--then fore-right--then this way, and then that, in all its
possible directions and fore-shortenings--he would have concluded my
uncle Toby had got hold of the medius terminus, and was syllogizing and
measuring with it the truth of each hypothesis of long noses, in order,
as my father laid them before him. This, by-the-bye, was more than my
father wanted--his aim in all the pains he was at in these philosophick
lectures--was to enable my uncle Toby not to discuss--but comprehend--to
hold the grains and scruples of learning--not to weigh them.--My uncle
Toby, as you will read in the next chapter, did neither the one or the
other.

Chapter 2.XXXIV.

'Tis a pity, cried my father one winter's night, after a three hours
painful translation of Slawkenbergius--'tis a pity, cried my father,
putting my mother's threadpaper into the book for a mark, as he
spoke--that truth, brother Toby, should shut herself up in such
impregnable fastnesses, and be so obstinate as not to surrender herself
sometimes up upon the closest siege.--

Now it happened then, as indeed it had often done before, that my uncle
Toby's fancy, during the time of my father's explanation of Prignitz to
him--having nothing to stay it there, had taken a short flight to the
bowling-green;--his body might as well have taken a turn there too--so
that with all the semblance of a deep school-man intent upon the medius
terminus--my uncle Toby was in fact as ignorant of the whole lecture,
and all its pros and cons, as if my father had been translating Hafen
Slawkenbergius from the Latin tongue into the Cherokee. But the word
siege, like a talismanic power, in my father's metaphor, wafting back
my uncle Toby's fan