Sherlock Holmes

"I have already explained to you that what is out of the
common is usually a guide rather than a hindrance.
In solving a problem of this sort, the grand thing is to be able
to reason backwards.  That is a very useful accomplishment,
and a very easy one, but people do not practise it much.
In the every-day affairs of life it is more useful to
reason forwards, and so the other comes to be neglected.
There are fifty who can reason synthetically for one who can
reason analytically."

"I confess," said I, "that I do not quite follow you."

"I hardly expected that you would.  Let me see if I can make
it clearer.  Most people, if you describe a train of events
to them, will tell you what the result would be.  They can
put those events together in their minds, and argue from them
that something will come to pass.  There are few people,
however, who, if you told them a result, would be able to
evolve from their own inner consciousness what the steps were
which led up to that result.  This power is what I mean when
I talk of reasoning backwards, or analytically."

-- Sherlock Holmes in A Study In Scarlet: Chapter VII Conclusion