it does not the less behove him, according to the measure of his
opportunities, to sift and scrutinize the details of every specific
experiment. Without this, he may be an excellent professor of abstract
science; for a person may be of great use who points out correctly what
effects will follow from certain combinations of possible circumstances,
in whatever tract of the extensive region of hypothetical cases those
combinations may be found. He stands in the same relation to the
legislator, as the mere geographer to the practical navigator; telling
him the latitude and longitude of all sorts of places, but not how to
find whereabouts he himself is sailing. If, however, he does no more
than this, he must rest contented to take no share in practical
politics; to have no opinion, or to hold it with extreme modesty, on
the applications which should be made of his doctrines to existing
circumstances.

No one who attempts to lay down propositions for the guidance of
mankind, however perfect his scientific acquirements, can dispense with
a practical knowledge of the actual modes in which the affairs of the
world are carried on, and an extensive personal experience of the actual
ideas, feelings, and intellectual and moral tendencies of his own
country and of his own age. The true practical statesman is he who
combines this experience with a profound knowledge of abstract political
philosophy. Either acquirement, without the other, leaves him lame and
impotent if he is sensible of the deficiency; renders him obstinate and
presumptuous if, as is more probable, he is entirely unconscious of it.

Such, then, are the respective offices and uses of the _a priori_ and
the _a posteriori_ methods--the method of abstract science, and that of
specific experiment--as well in Political Economy, as in all the other
branches of social philosophy. Truth compels us to express our
conviction that whether among those who have written on, these subjects,
or among those for whose use they wrote, few can be pointed out who have
allowed to each of these methods its just value, and systematically kept
each to its proper objects and functions. One of the peculiarities of
modern times, the separation of theory from practice--of the studies of
the closet, from the outward business of the world--has given a wrong
bias to the ideas and feelings both of the student and of the man of
business. Each undervalues that part of the materials of thought with
whi