ays implied in the first. When it is said, "Do this for me,
and I will do that for you," an exchange of service for service is
proposed. Again, when it is said, "Give me this, and I will give you
that," it is the same as saying, "I yield to you what I have done, yield
to me what you have done." The labour is past, instead of present; but
the exchange is not the less governed by the comparative valuation of
the two services: so that it is quite correct to say that the principle
of _value_ is in the services rendered and received on account of the
productions exchanged, rather than in the productions themselves.

In reality, services are scarcely ever exchanged directly. There is a
medium, which is termed _money_. Paul has completed a coat, for which he
wishes to receive a little bread, a little wine, a little oil, a visit
from a doctor, a ticket for the play, &c. The exchange cannot be
effected in kind, so what does Paul do? He first exchanges his coat for
some money, which is called _sale_; then he exchanges this money again
for the things which he wants, which is called _purchase_; and now,
only, has the reciprocity of services completed its circuit; now, only,
the labour and the compensation are balanced in the same individual,--"I
have done this for society, it has done that for me." In a word, it is
only now that the exchange is actually accomplished. Thus, nothing can
be more correct than this observation of J. B. Say:--"Since the
introduction of money, every exchange is resolved into two elements,
_sale_ and _purchase_. It is the reunion of these two elements which
renders the exchange complete."

We must remark, also, that the constant appearance of money in every
exchange has overturned and misled all our ideas: men have ended in
thinking that money was true riches, and that to multiply it was to
multiply services and products. Hence the prohibitory system; hence
paper money; hence the celebrated aphorism, "What one gains the other
loses;" and all the errors which have ruined the earth, and embrued it
with blood.[2] After much research it has been found, that in order to
make the two services exchanged of equivalent value, and in order to
render the exchange _equitable_, the best means was to allow it to be
free. However plausible, at first sight, the intervention of the State
might be, it was soon perceived that it is always oppressive to one or
other of the contracting parties. When we look into these subjects