. The scientific investigator who notes a
new phenomenon may be utterly ignorant of its cause, but he will,
without hesitation, seek for that cause. If you ask him why he does so,
he will probably say that it must have had a cause; and thereby imply
that his belief in causation is a necessary belief.

In the _Treatise_ Hume indeed takes the bull by the horns:

" ... as all distinct ideas are separable from each other, and as
the ideas of cause and effect are evidently distinct, 'twill be
easy for us to conceive any object to be non-existent this moment
find existent the next, without conjoining to it the distinct idea
of a cause or productive principle."--(I. p. 111.)

If Hume had been content to state what he believed to be matter of fact,
and had abstained from giving superfluous reasons for that which is
susceptible of being proved or disproved only by personal experience,
his position would have been stronger. For it seems clear that, on the
ground of observation, he is quite right. Any man who lets his fancy run
riot in a waking dream, may experience the existence at one moment, and
the non-existence at the next, of phenomena which suggest no connexion
of cause and effect. Not only so, but it is notorious that, to the
unthinking mass of mankind, nine-tenths of the facts of life do not
suggest the relation of cause and effect; and they practically deny the
existence of any such relation by attributing them to chance. Few
gamblers but would stare if they were told that the falling of a die on
a particular face is as much the effect of a definite cause as the fact
of its falling; it is a proverb that "the wind bloweth where it
listeth;" and even thoughtful men usually receive with surprise the
suggestion, that the form of the crest of every wave that breaks,
wind-driven, on the sea-shore, and the direction of every particle of
foam that flies before the gale, are the exact effects of definite
causes; and, as such, must be capable of being determined, deductively,
from the laws of motion and the properties of air and water. So again,
there are large numbers of highly intelligent persons who rather pride
themselves on their fixed belief that our volitions have no cause; or
that the will causes itself, which is either the same thing, or a
contradiction in terms.

Hume's argument in support of what appears to be a true proposition,
however, is of the circular sort, for the major premiss, that a