PREFACE vii

while the nature of the energy applied to their investigation

is essentially one, it is evident that the groundwork of science

must be sought in the human mind, and in the mind of each

individual man who applies himself to its study the study

of epistemology.*

Now the mind of each one of us is, during our waking

hours, ceaselessly active, but active in very different ways.

We may be vaguely conscious of our existence while listen-

ing to some sweet melody which entrances us with its charm.

\Ve may be enjoying the freshness of the air and the

augmenting brightness of the sun of a summer's day, hardly

aware of undefined thoughts passing through our mind. We

may be anxiously longing for the arrival of a friend whom we

impatiently expect, or dreading the delay in his arrival as

foreboding evil. We may be dwelling in fancy over events

of days gone by, or looking forward to the future fruition of

a hope long entertained. We may be simultaneously apply-

ing our senses of sight and touch to ascertain the shape and

structure of some material object a feather, a shell, or a

work of art. We may be carrying out a piece of deductive

reasoning, or we may be reflecting upon what we are about,

and making sure we know, suspect, or doubt what we are

actually cognizing, suspecting, or doubting. But if we happen

to be engaged in the study and pursuit of science, we must

be aware what we are doing, and, at least occasionally, reflect

upon our perceptions.

Therefore, once more, the groundwork of science must be

sought for in the human mind in our own mind when

cognizing scientific truths ; especially those deemed most

certain and far-reaching. And such truths cannot be truths

gained by reasoning, and cannot depend for their certainty

on any experiments or observations alone. Such is manifestly

the case, since whatever truth depends on reasoning cannot

/, understanding, and \^yos, a discourse.

while the nature of the energy applied to their investigation

is essentially one, it is evident that the groundwork of science

must be sought in the human mind, and in the mind of each

individual man who applies himself to its study the study

of epistemology.*

Now the mind of each one of us is, during our waking

hours, ceaselessly active, but active in very different ways.

We may be vaguely conscious of our existence while listen-

ing to some sweet melody which entrances us with its charm.

\Ve may be enjoying the freshness of the air and the

augmenting brightness of the sun of a summer's day, hardly

aware of undefined thoughts passing through our mind. We

may be anxiously longing for the arrival of a friend whom we

impatiently expect, or dreading the delay in his arrival as

foreboding evil. We may be dwelling in fancy over events

of days gone by, or looking forward to the future fruition of

a hope long entertained. We may be simultaneously apply-

ing our senses of sight and touch to ascertain the shape and

structure of some material object a feather, a shell, or a

work of art. We may be carrying out a piece of deductive

reasoning, or we may be reflecting upon what we are about,

and making sure we know, suspect, or doubt what we are

actually cognizing, suspecting, or doubting. But if we happen

to be engaged in the study and pursuit of science, we must

be aware what we are doing, and, at least occasionally, reflect

upon our perceptions.

Therefore, once more, the groundwork of science must be

sought for in the human mind in our own mind when

cognizing scientific truths ; especially those deemed most

certain and far-reaching. And such truths cannot be truths

gained by reasoning, and cannot depend for their certainty

on any experiments or observations alone. Such is manifestly

the case, since whatever truth depends on reasoning cannot

/, understanding, and \^yos, a discourse.