are venomous,' but only that those are venomous that
have a certain structure of fang; a point which he did not stay to
examine.

The discovery of an analogy, then, may suggest hypotheses; it states a
problem--to find the causes of the analogy; and thus it may lead to
scientific proof; but merely analogical argument is only probable in
various degrees. (1) The greater the number and importance of the points
of agreement, the more probable is the inference. (2) The greater the
number and importance of the points of difference, the less probable is
the inference. (3) The greater the number of unknown properties in the
subject of our argument, the less the value of any inference from those
that we do know. Of course the number of unknown properties can itself
be estimated only by analogy. In the case of Mars, they are probably
very numerous; and, apart from the evidence of canals, the prevalent
assumption that there are intelligent beings in that planet, seems to
rest less upon probability than on a curiously imaginative extension of
the gregarious sentiment, the chilly discomfort of mankind at the
thought of being alone in the universe, and a hope that there may be
conversable and 'clubable' souls nearer than the Dog-star.

CHAPTER XX

PROBABILITY

Sec. 1. Chance was once believed to be a distinct power in the world,
disturbing the regularity of Nature; though, according to Aristotle, it
was only operative in occurrences below the sphere of the moon. As,
however, it is now admitted that every event in the world is due to some
cause, if we can only trace the connection, whilst nevertheless the
notion of Chance is still useful when rightly conceived, we have to find
some other ground for it than that of a spontaneous capricious force
inherent in things. For such a conception can have no place in any
logical interpretation of Nature: it can never be inferred from a
principle, seeing that every principle expresses an uniformity; nor,
again, if the existence of a capricious power be granted, can any
inference be drawn from it. Impossible alike as premise and as
conclusion, for Reason it is nothing at all.

Every event is a result of causes: but the multitude of forces and the
variety of collocations being immeasurably great, the overwhelming
majority of events occurring about the same time are only related by
Causation so remotely that the connection cannot be followed. Whilst my
pen moves along the paper, a cab