when
they had laid down certain principles which belong properly to the
prolegomena of the science, and which are very useful when regarded as
providing logical tests of valid reasoning, they imagined that they had
done a great deal more, and that the desired science was actually
constituted. They laid down three or four primary axioms, such as the
doctrine that men desire wealth, and fancied that the whole theory
could be deduced from them. This, if what I have said be true, was
really to misunderstand what they were really doing. It was to suppose
that you could obtain a description of social phenomena without
examining the actual structure of society; and was as erroneous as to
suppose that you could deduce physiological truths from a few general
propositions about the mechanical relations of the skeleton. Such
criticisms have been made by the historical school of Economists; and
I, at least, can fully accept their general view. I quite agree that
the old assumptions of the older school were frequently unjustifiable;
nor can I deny that they laid them down with a tone of superlative
dogmatism, which was apt to be very offensive, and which was not
justified by their position. Moreover, I entirely agree that the
progress of economic science, and of all other moral sciences, requires
a historical basis; and that we should make a very great blunder if we
thought that the creation of an economic man would justify us in
dispensing with an investigation of concrete facts, both of the present
day and of earlier stages of industrial evolution. But to this there is
an obvious qualification. What do we mean by investigating facts? It
seems to be a very simple rule, but it leads us at once to great
difficulties. So, as Mill and later writers have very rightly asked,
how are we to settle even the most obvious questions in inquiries
where, for obvious reasons, we cannot make experiments, and where we
have not such a set of facts as would spontaneously give us the truths
which we might seek by experiment? Take, as Mill suggested, such a
question as free trade. We cannot get two countries alike in all else,
and differing only in respect to their adoption or rejection of a
protective tariff. Anything like a thoroughgoing system of free trade
has been tried in England alone; and the commercial prosperity of the
country since its adoption has been affected by innumerable conditions,
so that it is altogether impossible to isolate the res