DENCE.

 (i) When, next, we come to apply the scholastic

doctrine of evidence as the supreme criterion of truth and ulti

mate motive of certitude to the five classes of judgments referred

to above (148), we shall find no special difficulty in the doctrine

as applied to mediate evidence for deductive inferences from

self-evident axioms of the ideal order. It will be admitted that

in such a purely deductive science as, for instance, mathematics,

if our conclusions are inferred in strict accordance with the

logical canons of formally correct deductive reasoning, then these

conclusions will give us a true or genuine insight into reality in

whatever sense the principles or axioms do so. Hence it is some

times said that conformity with axioms or principles > as standards,

is the test or criterion of the truth of such conclusions. And

again it is said that the logical canons of formally correct inference

are also tests or criteria of the truth of such conclusions : inas

much as the intellect, as long as it is guided by such canons, will

derive from the principles only what is really involved in them.

Both statements are correct. The self-evidence of the principles

is the norma or standard by conformity with which the con

clusions are known to be evident and therefore true. And the

canons of inference are means of realizing this conformity. They

are, in a sense, tests of evidence : i.e. they help the intellect to

test mediate evidence by resolving it into, and showing its con

tinuity with, immediate evidence. For at least in regard to

judgments which are not immediately evident the intellect may

err by mistaking apparent evidence for real evidence : and the

canons of inference help it to avoid such mistakes.

1 Cf. Science of Logic, ii., 260. For the criteria and sources of historical

knowledge and certitude, cf. ibid., 261.

264 THEOK V OF KNO IV LEDGE

In regard to deductive inference there is one point to be

noted when we pass from the abstract domain of pure or rational

demonstration to the concrete domain of mixed and empiric de

monstration. 1 In this domain we are applying abstract prin

ciples to concrete facts, and assuming that the facts really

embody the principles : i.e. we are assuming the truth of some

form of Realism as against Conceptualism and Nominalism.

Therefore the mediate evidence on which the certitude of our

conclusions is based includes the evidence on which the truth

of Realism is grounded. In other words, we know that these

conclusions give us a true and genuine insight into reality only

because and in so far as we are certain that our abstract concepts

and principles are validly applicable to the concrete domain of

our sense experience.

It will also be admitted that for the whole domain of scientific

conclusions from purely rational principles, intrinsic evidence,

mediate or immediate, must be forthcoming before the mind can

give an assent of science to such judgments. If the individual

mind accepts them as true merely on the extrinsic evidence of

human testimony, its assent is not an assent of science but of

belief or faith. It is only right and reasonable to seek for their

intrinsic evidence before assenting to them. In view of the

persistent misrepresentation of scholasticism as teaching that

even in the domain of purely rational truths authority is the

ultimate basis of human certitude, we can only reiterate the

genuine teaching of scholasticism that in this domain the appeal

to authority is the weakest of all arguments.- Of course, when

an individual investigator derives some remote conclusion by

a long and sustained effort of deductive reasoning from first

principles, his assent to such a conclusion will be strengthened

when he learns that other investigators have reached the same

conclusion independently : conscious as he is of his own falli

bility, this corroborative testimony will assure him that he has

avoided mistakes and reasoned correctly. In this sense it may

be admitted that in the domain of purely rational, scientific

investigation human testimony is a "confirming criterion" of

truth.

1 Cf. Science of Logic, ii., 254 (r), p. 234.

2 " Locus ab auctoritate quae fundatur super ratione humana est infirmis-

simus." ST./THOMAS, Sitmtna TheoL, I., Q. i., a. S, ad 2. Cf. Science of Logic, ii.,

pp. 251-2, for references to sources.

TRUTH AND EVIDENCE 265

(2) All that has just been said about the scholastic doctrine

of evidence as applied to deductions from principles is equally

true of the same doctrine as applied to inductive generalizations

from the individual facts of immediate sense experience. The

Logic of Induction analyses the whole complex process whereby

we can trace back to the immediate evidence for our interpreta

tions of individual sense data the mediate evidence we have for

inductively established laws or generalizations ; it teaches us

how to evaluate this evidence; it lays down the canons in

accordance with which we reach physical or moral certitude

about those generalizations through such evidence ; it explores

the scope and significance of the principle known as the Uni

formity of Nature ) which is involved in all inductive generaliza

tion from individual facts or phenomena ; and it brings to light

the ultimate rational grounds which justify our assent to this

principle. 1 Hence all such general judgments as we can

establish by induction, all generalizations for which we have

sufficient (mediate) evidence to warrant a firm or certain assent,

will be true, or genuinely representative of reality, in whatever

sense the self-evident principles of reason and the self-evident inter

pretations of sense facts are representative of reality.

(3) Thirdly, our certitude about judgments which we receive

on authority, on extrinsic evidence, is ultimately dependent on

the immediate intrinsic evidence we have for the trustworthiness

of the authority in each particular case. And not on that alone :

but also on the sufficiency of the grounds or evidence which we

have for our general spontaneous conviction that human testi

mony can be found to be really endowed with the characteristics

of " knowledge " and " veracity " which make it trustworthy. But

this latter conviction is based on repeated actual verifications of

the trustworthiness of human testimony by the presence of im

mediate, intrinsic evidence for the truth of the judgments which

that testimony has vouched for.

 (i) When, next, we come to apply the scholastic

doctrine of evidence as the supreme criterion of truth and ulti

mate motive of certitude to the five classes of judgments referred

to above (148), we shall find no special difficulty in the doctrine

as applied to mediate evidence for deductive inferences from

self-evident axioms of the ideal order. It will be admitted that

in such a purely deductive science as, for instance, mathematics,

if our conclusions are inferred in strict accordance with the

logical canons of formally correct deductive reasoning, then these

conclusions will give us a true or genuine insight into reality in

whatever sense the principles or axioms do so. Hence it is some

times said that conformity with axioms or principles > as standards,

is the test or criterion of the truth of such conclusions. And

again it is said that the logical canons of formally correct inference

are also tests or criteria of the truth of such conclusions : inas

much as the intellect, as long as it is guided by such canons, will

derive from the principles only what is really involved in them.

Both statements are correct. The self-evidence of the principles

is the norma or standard by conformity with which the con

clusions are known to be evident and therefore true. And the

canons of inference are means of realizing this conformity. They

are, in a sense, tests of evidence : i.e. they help the intellect to

test mediate evidence by resolving it into, and showing its con

tinuity with, immediate evidence. For at least in regard to

judgments which are not immediately evident the intellect may

err by mistaking apparent evidence for real evidence : and the

canons of inference help it to avoid such mistakes.

1 Cf. Science of Logic, ii., 260. For the criteria and sources of historical

knowledge and certitude, cf. ibid., 261.

264 THEOK V OF KNO IV LEDGE

In regard to deductive inference there is one point to be

noted when we pass from the abstract domain of pure or rational

demonstration to the concrete domain of mixed and empiric de

monstration. 1 In this domain we are applying abstract prin

ciples to concrete facts, and assuming that the facts really

embody the principles : i.e. we are assuming the truth of some

form of Realism as against Conceptualism and Nominalism.

Therefore the mediate evidence on which the certitude of our

conclusions is based includes the evidence on which the truth

of Realism is grounded. In other words, we know that these

conclusions give us a true and genuine insight into reality only

because and in so far as we are certain that our abstract concepts

and principles are validly applicable to the concrete domain of

our sense experience.

It will also be admitted that for the whole domain of scientific

conclusions from purely rational principles, intrinsic evidence,

mediate or immediate, must be forthcoming before the mind can

give an assent of science to such judgments. If the individual

mind accepts them as true merely on the extrinsic evidence of

human testimony, its assent is not an assent of science but of

belief or faith. It is only right and reasonable to seek for their

intrinsic evidence before assenting to them. In view of the

persistent misrepresentation of scholasticism as teaching that

even in the domain of purely rational truths authority is the

ultimate basis of human certitude, we can only reiterate the

genuine teaching of scholasticism that in this domain the appeal

to authority is the weakest of all arguments.- Of course, when

an individual investigator derives some remote conclusion by

a long and sustained effort of deductive reasoning from first

principles, his assent to such a conclusion will be strengthened

when he learns that other investigators have reached the same

conclusion independently : conscious as he is of his own falli

bility, this corroborative testimony will assure him that he has

avoided mistakes and reasoned correctly. In this sense it may

be admitted that in the domain of purely rational, scientific

investigation human testimony is a "confirming criterion" of

truth.

1 Cf. Science of Logic, ii., 254 (r), p. 234.

2 " Locus ab auctoritate quae fundatur super ratione humana est infirmis-

simus." ST./THOMAS, Sitmtna TheoL, I., Q. i., a. S, ad 2. Cf. Science of Logic, ii.,

pp. 251-2, for references to sources.

TRUTH AND EVIDENCE 265

(2) All that has just been said about the scholastic doctrine

of evidence as applied to deductions from principles is equally

true of the same doctrine as applied to inductive generalizations

from the individual facts of immediate sense experience. The

Logic of Induction analyses the whole complex process whereby

we can trace back to the immediate evidence for our interpreta

tions of individual sense data the mediate evidence we have for

inductively established laws or generalizations ; it teaches us

how to evaluate this evidence; it lays down the canons in

accordance with which we reach physical or moral certitude

about those generalizations through such evidence ; it explores

the scope and significance of the principle known as the Uni

formity of Nature ) which is involved in all inductive generaliza

tion from individual facts or phenomena ; and it brings to light

the ultimate rational grounds which justify our assent to this

principle. 1 Hence all such general judgments as we can

establish by induction, all generalizations for which we have

sufficient (mediate) evidence to warrant a firm or certain assent,

will be true, or genuinely representative of reality, in whatever

sense the self-evident principles of reason and the self-evident inter

pretations of sense facts are representative of reality.

(3) Thirdly, our certitude about judgments which we receive

on authority, on extrinsic evidence, is ultimately dependent on

the immediate intrinsic evidence we have for the trustworthiness

of the authority in each particular case. And not on that alone :

but also on the sufficiency of the grounds or evidence which we

have for our general spontaneous conviction that human testi

mony can be found to be really endowed with the characteristics

of " knowledge " and " veracity " which make it trustworthy. But

this latter conviction is based on repeated actual verifications of

the trustworthiness of human testimony by the presence of im

mediate, intrinsic evidence for the truth of the judgments which

that testimony has vouched for.