y about
empirical uniformities, except that we may infer from them with some
degree of reasonable probability, and that if we want ground for a
more certain inference we should try to explain them.

CHAPTER II.

ASCERTAINMENT OF SIMPLE FACTS IN THEIR ORDER.--PERSONAL OBSERVATION.
--HEARSAY EVIDENCE--METHOD OF TESTING TRADITIONAL EVIDENCE.

All beliefs as to simple matter of fact must rest ultimately on
observation. But, of course, we believe many things to have happened
that we have never seen. As Chaucer says:--

But God forbede but men shoulde 'lieve
Wel more thing than men han seen with eye.
Man shall not weenen everything a lie
But if himself it seeth or else doth.

For the great bulk of matters of fact that we believe we are
necessarily dependent on the observations of others. And if we are
to apply scientific method to the ascertainment of this, we must know
what errors we are liable to in our recollections of what we have
ourselves witnessed, and what errors are apt to arise in the tradition
of what purports to be the evidence of eye-witnesses.

I.--PERSONAL OBSERVATION.

It is hard to convince anybody that he cannot trust implicitly to his
memory of what he has himself seen. We are ready enough to believe
that others may be deceived: but not our own senses. Seeing is
believing. It is well, however, that we should realise that all
observation is fallible, even our own.

Three great besetting fallacies or tendencies to error may be
specified:--

1. Liability to have the attention fastened on special incidents, and
so diverted from other parts of the occurrence.

2. Liability to confuse and transpose the sequence of events.

3. Liability to substitute inference for fact.

It is upon the first of these weaknesses in man as an observing
machine that jugglers chiefly depend on working their marvels. Sleight
of hand counts for much, but diverting the spectator's eyes for a good
deal more. That is why they have music played and patter incessantly
as they operate. Their patter is not purposeless: it is calculated to
turn our eyes away from the movements of their nimble hands.

It must be borne in mind that in any field of vision there are many
objects, and that in any rapid succession of incidents much more
passes before the eyes than the memory can retain in its exact
order. It is of course in moments of excitement and hurry, when our
observation is distracted, that we are most subject