Economics in One Lesson

Part Three:
The Lesson Restated 
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1
E
conomics, as we have now seen again and again, is a science of
recognizing 
secondary
consequences. It is also a science of seeing
general
consequences. It is the science of tracing the effects of some
proposed or existing policy not only on some 
special
interest 
in the short
run,
but on the 
general
interest 
in the long run
.
This is the lesson that has been the special concern of this book.
We stated it first in skeleton form, and then put flesh and skin on it
through more than a score of practical applications.
But in the course of specific illustration we have found hints of
other general lessons; and we should do well to state these lessons to
ourselves more clearly.
In seeing that economics is a science of tracing consequences, we
must have become aware that, like logic and mathematics, it is a sci-
ence of recognizing inevitable 
implications
.
We may illustrate this by an elementary equation in algebra. Sup-
pose we say that if
x
= 5 then 
x
+ 
y
= 12. The “solution” to this equa-
tion is that 
y
equals 7; but this is so precisely because the equation 
tells
us in effect that 
y
equals 7. It does not make that assertion directly, but
it inevitably implies it.
What is true of this elementary equation is true of the most com-
plicated and abstruse equations encountered in mathematics.
The