2. CHAPTER II. THE SCIENCE OF DEDUCTION.
"You see," he explained, "I consider that a man's brain
originally is like a little empty attic, and you have to
stock it with such furniture as you choose. A fool takes in
all the lumber of every sort that he comes across, so that
the knowledge which might be useful to him gets crowded out,
or at best is jumbled up with a lot of other things so that
he has a difficulty in laying his hands upon it. Now the
skilful workman is very careful indeed as to what he takes
into his brain-attic. He will have nothing but the tools
which may help him in doing his work, but of these he has
a large assortment, and all in the most perfect order.
It is a mistake to think that that little room has elastic
walls and can distend to any extent. Depend upon it there comes
a time when for every addition of knowledge you forget something
that you knew before. It is of the highest importance, therefore,
not to have useless facts elbowing out the useful ones."
"But the Solar System!" I protested.
"What the deuce is it to me?" he interrupted impatiently;
"you say that we go round the sun. If we went round the moon it
would not make a pennyworth of difference to me or to my work."
I was on the point of asking him what that work might be,
but something in his manner showed me that the question would
be an unwelcome one. I pondered over our short conversation,
however, and endeavoured to draw my deductions from it.
He said that he would acquire no knowledge which did not bear
upon his object. Therefore all the knowledge which he
possessed was such as would be useful to him. I enumerated
in my own mind all the various points upon which he had shown
me that he was exceptionally well-informed. I even took a
pencil and jotted them down. I could not help smiling at the
document when I had completed it. It ran in this way --
SHERLOCK HOLMES -- his limits.