ld not have affected the circumstances in question.
Suppose, for example, our question is whether the Education Act
of 1872 had an influence in the decrease of juvenile crime. Such a
decrease took place _post hoc_; was it _propter hoc_? We may at once
eliminate or put out of account the abolition of Purchase in the Army
or the extension of the Franchise as not having possibly exercised any
influence on juvenile crime. But with all such eliminations, there may
still remain other possible influences, such as an improvement in
the organisation of the Police, or an expansion or contraction in
employment. "Can you tell me in the face of chronology," a leading
statesman once asked, "that the Crimes Act of 1887 did not diminish
disorder in Ireland?" But chronological sequence alone is not a proof
of causation as long as there are other contemporaneous changes of
condition that may also have been influential.

The great source of fallacy is our proneness to eliminate or isolate
in accordance with our prejudices. This has led to the gibe that
anything can be proved by statistics. Undoubtedly statistics may be
made to prove anything if you have a sufficiently low standard of
proof and ignore the facts that make against your conclusion. But
averages and variations in them are instructive enough if handled with
due caution. The remedy for rash conclusions from statistics is not no
statistics, but more of them and a sound knowledge of the conditions
of reasonable proof.

II.--THE PRESUMPTION FROM EXTRA-CASUAL COINCIDENCE.

We have seen that repeated coincidence raises a presumption of causal
connexion between the coinciding events. If we find two events going
repeatedly together, either abreast or in sequence, we infer that the
two are somehow connected in the way of causation, that there is a
reason for the coincidence in the manner of their production. It may
not be that the one produces the other, or even that their causes are
in any way connected: but at least, if they are independent one of the
other, both are tied down to happen at the same place and time,--the
coincidence of both with time and place is somehow fixed.

But though this is true in the main, it is not true without
qualification. We expect a certain amount of repeated coincidence
without supposing causal connexion. If certain events are repeated
very often within our experience, if they have great positive
frequency, we may observe them happening together mo