_APPLICATION OF THE CALCULUS OF PROBABILITIES TO THE MORAL SCIENCES._
We have just seen the advantages of the analysis of probabilities in the
investigation of the laws of natural phenomena whose causes are unknown
or so complicated that their results cannot be submitted to calculus.
This is the case of nearly all subjects of the moral sciences. So many
unforeseen causes, either hidden or inappreciable, influence human
institutions that it is impossible to judge _à priori_ the results. The
series of events which time brings about develops these results and
indicates the means of remedying those that are harmful. Wise laws have
often been made in this regard; but because we had neglected to conserve
the motives many have been abrogated as useless, and the fact that
vexatious experiences have made the need felt anew ought to have
reëstablished them.
It is very important to keep in each branch of the public administration
an exact register of the results which the various means used have
produced, and which are so many experiences made on a large scale by
governments. Let us apply to the political and moral sciences the method
founded upon observation and upon calculus, the method which has served
us so well in the natural sciences. Let us not offer in the least a
useless and often dangerous resistance to the inevitable effects of the
progress of knowledge; but let us change only with an extreme
circumspection our institutions and the usages to which we have already
so long conformed. We should know well by the experience of the past the
difficulties which they present; but we are ignorant of the extent of
the evils which their change can produce. In this ignorance the theory
of probability directs us to avoid all change; especially is it
necessary to avoid the sudden changes which in the moral world as well
as in the physical world never operate without a great loss of vital
force.
Already the calculus of probabilities has been applied with success to
several subjects of the moral sciences. I shall present here the
principal results.