the case of the sale of the use of money. The last matter with which
we shall deal is the machinery by which exchanges are conducted,
namely, money. Many other subjects, such as slavery and the legitimacy
of commerce, will be treated as they arise in the course of our
treatment of these principal divisions.

In its ultimate analysis, the whole subject may be reduced to a
classification of the various duties which attached to the right of
private property. The owner of property, as we shall see, was bound
to observe certain duties in respect of its acquisition and its
consumption, and certain other duties in respect of its exchange,
whether it consisted of goods or of money. The whole fabric of
mediæval economics was based on the foundation of private property;
and the elaborate and logical system of regulations to ensure justice
in economic life would have had no purpose or no use if the subject
matter of that justice were abolished.

It must not be understood that the mediæval writers treated economic
subjects in this order, or in any order at all. As we have already
said, economic matters are simply referred to in connection with
ethics, and were not detached and treated as making up a distinct
body of teaching. Ashley says: 'The reader will guard himself against
supposing that any mediæval writer ever detached these ideas from
the body of his teaching, and put them together as a modern text-book
writer might do; or that they were ever presented in this particular
order, and with the connecting argument definitely stated.'[1]

[Footnote 1: _Op. cit._, vol. i. pt. ii. p. 387.]