71. The second part of logic, which has for its object the end of reasoning, that is, science in general, treats: 1. of the different states of the intellect in respect to truth; 2. of demonstration; 3. of science in general and of its divisions. -- Before treating of science in itself, and the way in which the sciences are divided and co-ordinated, it is well to examine: 1. What truth is, which is the object of science, and what are the different states of the intellect in respect to truth; 2. What produces science, viz., demonstration.
ART. I. -- TRUTH.
72. Truth is the conformity between the intellect and the thing known by it. -- I judge that God is good; this judgment corresponds to what God is in reality; hence it is true, In the same way, every creature corresponds to the idea which God has of it; that is, every creature is true.
73. Truth is metaphysical, logical, or moral. -- Truth is in the thing, in our cognition of the thing, or in our expression of a cognition. In the first case, it is the conformity of the thing to the divine intellect this is ontological or metaphysical truth. In the second case, it is the conformity of our intellect to the thing known; this is truth of cognition or logical truth.
Logical truth, according to its object, is of the spiritual or corporeal order, general or particular, natural or supernatural. To metaphysical and logical truth is added moral truth or veracity, which is the conformity of speech or other external sign to the thought in one's mind. The opposite of moral truth is a lie. Moral truth depends on logical truth, as the latter depends on metaphysical truth.
74. The opposite of logical truth is falsity; metaphysical truth has no opposite. -- Our intellect is not the cause of creatures, and the knowledge which it acquires of them may represent them differently from what they are. There may, therefore, exist in our intellect logical falsity or error. The divine intellect, on the contrary, being the cause of everything that is, every being is necessarily such as God knows it; every being, therefore, must necessarily be metaphysically true. Hence being and metaphysical truth are convertible and may be affirmed of each other; and it may be said that whatever is is true, and whatever is true is, and that God, the absolute Being, is also the absolute Truth.
ART. II. -- IN WHAT OPERATION OF THE INTELLECT LOGICAL TRUTH IS FOUND.
75. Logical truth is, properly speaking, found only in the act of judgment. -- Logical truth is a correspondence between the intellect and the thing known by it; it can, therefore, strictly speaking, be found only in that operation of the intellect which perceives and expresses this correspondence, that is, in the act of judgment. Moreover, truth is the perfection of cognition, and therefore is not, strictly speaking, to be found in simple apprehension, which is imperfect and inchoate cognition.
76. Truth is not properly in simple apprehension nor in sensation. -- Every cognitive faculty, put in presence of its object, must apprehend the object as it is. Hence by simple apprehension and by sensation, things are known as they are, and this knowledge is materially true or conformed to the thing. But as the intellect has no cognition of this conformity, since there is no judgment, it follows that there is not, in simple apprehension or sensation, formal truth or truth properly so called.
ART. III. -- DIFFERENT STATES OF THE INTELLECT IN RESPECT TO TRUTH.
77. There are three different states of the intellect in respect to truth 1. Certitude, 2. Opinion or probability, 3. Doubt. -- Certitude is that state of the intellect in which it firmly adheres to a known truth without fear that the contrary may be true.
Opinion is that state of the intellect in which it adheres to something known, but with fear that the contrary may be true.
Doubt is that state of the intellect in which it is in suspense and adheres neither to the affirmative nor the negative of the thing proposed. Doubt is negative when the intellect perceives no motive to adhere either to the affirmative or the negative: doubt is positive when the intellect has as strong motives for adhering to the affirmative as to the negative.
78. Probability, whatever its degree, is specifically distinct from certitude. -- Probability holds a middle place between doubt and certitude; it is susceptible of increase and diminution and may have several degrees; but none of these degrees, however great, will constitute certitude. This latter, on the contrary, cannot admit of degrees; it is or it is not. The calculation of probabilities has its foundation in the ascertained relation existing between the probable thing and its contrary. This calculation confined within proper bounds may become a legitimate source of knowledge, on which are based certain social institutions, such as insurance companies.{1}
79. The elements of certitude being, 1. The truth of the object, 2. the firmness of adherence, 3. the motive which produces this adherence, it may be divided according to the particular element in reference to which it is considered. -- Relatively to the truth of the object, certitude is common or philosophical, immediate or mediate, according as it is without, or with explicit cognition of the motive of adherence, known by intuition or by means of reasoning.
In respect to the firmness of adherence, it is to be remarked that while this adherence always excludes doubt, it may be more or less perfect according to the perfection of the motive producing it; we have, therefore, certainty of evidence, which is produced by an intrinsic motive, and certainty of faith, which is produced by an extrinsic motive.
Certainty of evidence is metaphysical, physical, or moral; for the intrinsic motive which produces it is nothing more than the perception of the connection existing between a subject and its attribute. But this connection belongs either to the metaphysical order, that is, is absolutely necessary, as, "Every effect must have a cause;" or to the physical order, as, "Fire burns;" or to the moral order, as, "Mothers love their children." In other words, the agreement or disagreement of subject and attribute is necessary according to (1) the very natnre of the things, or according to the laws (2) of the physical or (3) of the moral world, established by God. Of these three kinds of certainty, the most excellent is metaphysical certainty, which being founded on the very nature of things, whose archetypes are the divine essence, allows of no exception. Physical certainty is not absolute, since it is based on the supposition that in this particular case God has not suspended the effect of the physical laws which he freely established. It, therefore, is perfectly consistent with miracles. Moral certainty implies the condition that the moral laws have been fully observed by the subject; but as the subject is a free agent, moral certainty cannot of itself generate certitude as to the individual, but only as to the class or species. Certainty of faith is divine or human, according as it rests on divine authority, as the Scriptural revelation, or on human authority, as the facts of history.
ART. IV. -- IGNORANCE, ERROR, AND THEIR CAUSES.
80. Ignorance is the absence of truth from the intellect. -- Ignorance and error have not been reckoned among the states of the intellect in respect to truth, since, instead of being cognitions of truth, they are respectively its absence and its negation.
81. The causes of ignorance are: 1. the limited nature of our intellect; 2. a want of intellectual culture. -- The first cause of ignorance arises from the very nature of man, who is essentially a finite being. To this cause may be referred the organic defects which, in certain men, impede the cognition of truth.
The second cause is the absence of intellectual culture. Truth is not infused into man; he must acquire it either by instruction from others or by his own efforts. If he has not been taught and does not himself labor to develop his intellectual faculties, he must remain in ignorance of many truths.
82. Error is the adhesion of the intellect to a false judgment, or a want of conformity between intellect and object. -- Since error is an adhesion to a false judgment, it can be found neither in the senses nor in simple apprehension, but solely in the intellect in an act of judgment. It would be wrong to regard error, with Cousin (1792-1867), as incomplete truth. What he calls incomplete truth is none the less a truth; whereas error is the opposite of truth.
83. The principal causes of error are: 1. Precipitancy of judgment; 2. Liveliness of imagination; 3. Prejudice; 4. Passion. -- Precipitancy of judgment consists in judging of a thing not sufficiently considered. It is remedied by attention and reflection.
The imagination often obscures truth by presenting too lively images of sensible things. Its excesses are corrected by keeping it under a severe control of reason.
Prejudices are judgments adopted without examination. A prudent man will weigh his prejudices in the balance of reason; he will not rashly reject them, neither will he blindly follow them.
The passions are the most fruitful source of our errors; they obscure the intellect and present things to it in the borrowed light of a badly regulated will. The remedy for this evil is found in virtue alone.
To these internal causes may be added external ones, as education, the school, the vices of language; all of which are remedied by a prudent scrutiny and a sincere love of truth. Bacon (1561-1626) has divided our errors into four classes: 1. Idols of the tribe, errors arising from the weakness of our common nature; 2. Idols of the den, errors arising from our individual character; 3. Idols of the market-place, errors resulting from the vices of language; 4. Idols of the theatre, errors of the school. Evidently the causes assigned by Bacon for our errors may be reduced to those already indicated.{2}
84. Man in his present condition cannot invariably avoid all error. -- If man always made use of his faculties in conformity with the laws imposed on him, he would not err. But, owing to his natural weakness, he is incapable of always conforming to these laws, and, consequently, of avoiding all error.
{1} The following are the rules for the calculation of probabilities:
{2} See Metaphysics of the School, vol. i., p. 461.