io 4 THE GROUNDWORK OF SCIENCE

which carry with them their own evidence, which are evident

in and by themselves. What is to be said in deprecation

or defence of this character of self-evident truthfulness thus

attributed to some propositions, we will see later on. What

is here to be noted is the fact that science can have neither

justification, development, nor even existence, unless it be

conceded that not only is the principle of inference valid,

but also that underlying true and valid inferences, there are,

and must be, in the last resort, certain truths, which are

made known to us by their own direct evidence, and need

no process of proof.

These are intuitive truths, directly apprehended by our

power of intellectual intuition.* And, indeed, it is perfectly

evident that the convictions which men of science arrive

at by means of their observations, experiments, and in-

ferences, are not blind convictions, which they are compelled

to arrive at they know not how or why. They are eminently

intelligent convictions, attained by a conscious and inten-

tional pursuit of truth, and of which those who hold them

can give a good account, assigning valid reasons for the

scientific faith which is in them.

Amongst the facts and truths thus self-evident are certain

evident principles of reasoning. Physical science is emphati-

cally experimental science. But every experiment carefully

performed implies a most important latent truth. For when

an experiment has shown us that anything is certain, as, for

example, that a newt's leg may grow again after amputation,

because one actually has so grown again, we shall find that

such certainty implies an a priori truth. It implies that if the

newt has come to have four legs once more, it cannot at the

very same time have only three legs. This remark may seem

almost absurdly trivial ; but it is impossible to make principles

of this kind too clear too plainly certain and inevitable

* See ante, pp. 14 and 47.

which carry with them their own evidence, which are evident

in and by themselves. What is to be said in deprecation

or defence of this character of self-evident truthfulness thus

attributed to some propositions, we will see later on. What

is here to be noted is the fact that science can have neither

justification, development, nor even existence, unless it be

conceded that not only is the principle of inference valid,

but also that underlying true and valid inferences, there are,

and must be, in the last resort, certain truths, which are

made known to us by their own direct evidence, and need

no process of proof.

These are intuitive truths, directly apprehended by our

power of intellectual intuition.* And, indeed, it is perfectly

evident that the convictions which men of science arrive

at by means of their observations, experiments, and in-

ferences, are not blind convictions, which they are compelled

to arrive at they know not how or why. They are eminently

intelligent convictions, attained by a conscious and inten-

tional pursuit of truth, and of which those who hold them

can give a good account, assigning valid reasons for the

scientific faith which is in them.

Amongst the facts and truths thus self-evident are certain

evident principles of reasoning. Physical science is emphati-

cally experimental science. But every experiment carefully

performed implies a most important latent truth. For when

an experiment has shown us that anything is certain, as, for

example, that a newt's leg may grow again after amputation,

because one actually has so grown again, we shall find that

such certainty implies an a priori truth. It implies that if the

newt has come to have four legs once more, it cannot at the

very same time have only three legs. This remark may seem

almost absurdly trivial ; but it is impossible to make principles

of this kind too clear too plainly certain and inevitable

* See ante, pp. 14 and 47.