As was pointed out above, the proem (Book I., cc. i-iii.) is a prelude
to the treatment of the whole subject covered by the _Ethics_ and the
_Politics_ together. It sets forth the purpose of the enquiry, describes
the spirit in which it is to be undertaken and what ought to be the
expectation of the reader, and lastly states the necessary conditions
of studying it with profit. The aim of it is the acquisition and
propagation of a certain kind of knowledge (science), but this knowledge
and the thinking which brings it about are subsidiary to a practical
end. The knowledge aimed at is of what is best for man and of the
conditions of its realisation. Such knowledge is that which in its
consumate form we find in great statesmen, enabling them to organise and
administer their states and regulate by law the life of the citizens
to their advantage and happiness, but it is the same kind of knowledge
which on a smaller scale secures success in the management of the family
or of private life.

It is characteristic of such knowledge that it should be deficient
in "exactness," in precision of statement, and closeness of logical
concatenation. We must not look for a mathematics of conduct. The
subject-matter of Human Conduct is not governed by necessary and uniform
laws. But this does not mean that it is subject to no laws. There
are general principles at work in it, and these can be formulated in
"rules," which rules can be systematised or unified. It is all-important
to remember that practical or moral rules are only general and always
admit of exceptions, and that they arise not from the mere complexity
of the facts, but from the liability of the facts to a certain
unpredictable variation. At their very best, practical rules state
probabilities, not certainties; a relative constancy of connection is
all that exists, but it is enough to serve as a guide in life. Aristotle
here holds the balance between a misleading hope of reducing the