70. We have studied, in Dialectics, the laws which govern the form of reasoning; in Critical Logic we are to examine the certainty of the propositions, i.e., of the matter of reasoning, and the validity of the reasoning process itself. For this purpose we are to consider: 1. The nature of certainty; 2. The existence of certainty; 3. The means of attaining certainty, and 3. The ultimate test or criterion of certainty.
71. Certainty is defined as that state of mind in which we firmly adhere to a truth, on account of motives that exclude all fear of error. To study its nature, we must examine: (a) The nature of truth and of its opposite, falsity; (b) The various states of our minds with regard to truth, and (c) The elements that make up certainty.
ARTICLE I. TRUTH AND FALSITY..
72. Truth denotes conformity between a mind and an object. This conformity may be differently viewed:
1. When we consider the knowledge of the mind as conformable to the object known, we have logical truth; thus we speak of 'true judgments,' 'a true understanding of a fact or of a theory,' etc.
2. When we consider an object as cognoscible, i.e., as conformable to real or possible knowledge, we have metaphysical truth. In this sense the truth of an object is really identical with the very being of the object, for an object is cognoscible inasmuch as it has being; therefore all things have metaphysical truth.
3. When we consider language as conformable to the knowledge of him who uses it, we have moral truth; thus we say: 'a true account,' 'a true statement,' etc. Logic treats of logical truth.
73. Falsity is the opposite of truth. The mere absence of truth is sometimes called negative falsity; but this is not falsity in the proper sense of the word. We never speak of metaphysical falsity, for all things have metaphysical truth: even a false coin is truly what it is, and cognoscible as such; when we call it 'false,' we use a figure of speech by which we mean 'calculated to deceive.' Logical falsity exists when there is something in the intellect which is -not conformable to the object; moral falsity, or falsehood, exists when there is something in the expression not conformable to what is in the mind.
74. Logical falsity may occur in a judgment in three ways: 1. The intellect may affirm something which is not in the object; as when it affirms that matter can think, or it counts six stars where there are but five.
2. It may affirm as real what is only apparent; e.g., that the sun moves around the earth.
3. It may deny what really is, e.g., the motion of the earth.
75. The terms 'true' and 'false' are chiefly applied to judgments and propositions. Still, a mere apprehension or idea may also be called true; for it contains conformity between the mind and an object. But a mere apprehension is never called 'a truth'; this expression is confined to a judgment or a proposition.
76. Thesis I. A mere apprehension, as such cannot be false.
Proof. A mere apprehension, as such, is merely a mental image of something real or possible (for we cannot have an image of something absolutely impossible, e.g., of a square circle nor of a mere nothing); but every image, as such, i.e., in as far as it is an image, is necessarily conformable to that of which it is the image; else it would not be the image of it. Therefore, inasmuch as it is an image at all, it is true, not false. A portrait may not resemble the person who sat for it, but it represents what it represents, and so far it is a true image.
77. If it be objected that we may have a wrong idea or notion of a thing, e.g., of a spirit, conceiving it as a being composed of thin air, we answer that our concept of a being composed of thin air is a true idea; for such a being is possible; but, if we go on to judge that such a being is what is called a spirit, we do more than conceive an idea -- we join two ideas, we pronounce a judgment. It is not then the mere apprehension but the judgment which is false.
But can we not have an idea to which no possible being corresponds, e.g., of a 'square circle'? We have ideas of 'square' and of 'circle'; but we cannot either imagine or conceive a square circle. If we proceed to form a judgment that these ideas are compatible with each other, the error is in our judgment, not in our apprehensions. We do not deny that many men have wrong ideas, e.g., of religion, of the Catholic Church, of indulgences, of literary excellence, of honor, etc.; but the falsity in those ideas is due to the false judgments which those ideas implicitly contain, not to the ideas as ideas. For instance, a man conceives of an indulgence as 'leave to commit sin,' and he judges that this is the meaning of the word in Catholic doctrine.
ARTICLE II. STATES OF THE MIND WITH REGARD TO TRUTH.
78. 1. Ignorance is the state of a mind to which the truth is not presented at all; thus, we are all ignorant whether the number of the stars is odd or even. Ignorance is vincible if it is in our power to remove it; else it is invincible.
2. Doubt is the state of a mind hesitating whether to assent to a truth or not. A positive doubt sees reasons for and against assent; a negative doubt sees no reasons for either side; it comes to the same as ignorance. A mere doubt inclines the mind to neither side; but doubt may be accompanied by suspicion or opinion.
3. Suspicion is the state of a mind which has more leaning to one judgment than to its contradictory, but still pronounces no judgment.
4. Opinion is the state of a mind pronouncing a judgment, but not without fear of error. The motives for assenting are called the probability of a judgment. Probability is said to be intrinsic when the motives for assent are drawn from the consideration of the matter; extrinsic, when they are drawn from the statements of other persons.
5. Certainty is the state of a mind assenting to a truth without fear of error. If this fear of error is excluded by motives which leave no room for reasonable doubt, we have certainty in the proper sense of the word; if the fear of error is excluded without such motives, we have certainty improperly so called. In the latter case, the fear of error is excluded by the free action of the will, which turns away the intellect from considering all reasons of doubt.
79. It is useful to distinguish speculative from practical judgments: the former regard the certainty of knowledge, e.g., "The bread before me is not poisoned"; the latter, the prudence of action, e.g., "I may eat that bread without further examination." We act prudently when we look for the best guidance of reason that circumstances allow; strict certainty cannot be had concerning every step of daily conduct.
80. Since prudence is not inconsistent with a possibility of error, there may be invincible error connected with prudent practical judgments; but all error is inconsistent with strict certainty, and there can be no invincible error connected with judgments which are strictly certain.
81. Error in judgments of any kind, speculative or practical, is always traceable to free will. It cannot, of course, be caused by the objective truth; nor can the intellect be necessitated to judge falsely, since its very essence consists in the power of knowing, i.e., grasping, truth. There remains only one possible cause of error, viz., man's freedom to embrace a proposition. The free will of man can often bend the intellect so to fix its attention on the probabilities of a proposition as to overlook all reasons to doubt, and thus form a false judgment, firmly adhering to it without fear of error: this is not certainty, however, in the proper sense of the word (No. 78. 5)
82. Error or falsity cannot strictly be predicated of ignorance, doubt, or suspicion; for these states of the mind neither affirm nor deny anything whatever. Ignorance may be culpable, doubt may be unreasonable, suspicion unfounded and rash; but none of these is properly called false. Error can be predicated of nothing but opinion and certainty improperly so styled, i.e., of that state of mind which excludes the fear of error by the force of the will.
83. While the will is the ultimate source of all error, there are various proximate sources; the chief are:
1. Prejudices, i.e. ,judgments formerly assented to without proper examination.
2. Imperfect teaching or false information regarding facts and principles.
3. Confusion of ideas, whether resulting from dulness, i.e., slowness to distinguish between things similar, or from present inattention, owing to fatigue, negligence, multiplicity of cares, etc.
4. Passion, i.e., violent desire or aversion, which prompts our will to accept as true what is pleasing to us.
5. Impatience to arrive at a conclusion, either because we are eager to act, or too conceited to doubt our judgment, or too vain to acknowledge our ignorance. From all this it is evident that virtue is favorable to the acquisition of sound knowledge.
6. Another frequent source of erroneous judgments in many persons is a diseased condition of the nervous system or a portion of it. This abnormal state of the body may give rise to a variety of phantasms so vividly presented to the mind as to prevent calm consideration of the reasons for or against the formation of a judgment.
ARTICLE III. THE ELEMENTS THAT MAKE UP CERTAINTY.
84. We have defined certainty proper as the state of mind in which we firmly adhere to truth, on account of motives which exclude all fear of error. Several elements are here combined: 1. Subjectively, i.e., considering the acts of the mind, we have a firm adhesion (a positive element), and the exclusion of all fear of error (a negative element). 2. Objectively, i.e., considering the object known, we have such a manifestation of a truth as is sufficient to exclude all fear of error. The subjective adhesion is caused by the objective manifestation of truth. It is called subjective certainty, the manifestation of the truth being designated as objective certainty.
85. When the mind reflects on the fact that it has this firm adhesion, its certainty is called reflex; when it does not reflect on this fact, its certainty is direct. Philosophical certainty does not differ from ordinary reflex certainty except in this, that it notices distinctly and scientifically the motives of adhesion to a truth.
86. If we examine objective certainty still further, we find that the truth manifested may be of three species, which give respectively three different names to certainty; viz.:
1. Certainty is called metaphysical when the mind sees that a proposition is essentially true because its contradictory would be absurd; in such a case an exception is absolutely impossible; e.g., "Virtue is praiseworthy," "A triangle has three sides."
2. Certainty is physical when a fact is seen to be so necessary, according to the laws of material nature, that no one but the Author of those laws can make an exception; e.g., "The dead do not return to life."
3. Certainty is moral when the mind sees that something is constantly and universally true in the conduct of men, although dependent on their free choice; e.g. "Serious men do not tell a falsehood on important points without weighty motives."
87. The term 'moral certainty' is often used in a looser sense to denote a strong probability; e.g., I have a moral certainty that this house is not on fire just now, though I have no real certainty on the subject.
88. Subjectively considered, all kinds of certainty are alike in the negative element, i.e., all exclude fear of error; but the positive element, i.e., the intensity of the mind's adhesion to the truth, may be more or less firm: in some cases, as in axioms, and generally in all that is immediately evident, the mind cannot doubt the agreement of subject and predicate. Thus, we cannot help seeing that a whole is greater than its parts, that some bodies exist, that virtue and vice differ from each other, etc. Even in many things that are only mediately evident we cannot entertain a doubt; e.g., no well-informed man can doubt that ancient Rome existed.
In many matters, however, we can refuse to admit the objective truth; and in others we even find it difficult to steady our attention sufficiently on the object to exclude all doubt.
Metaphysical certainty admitting no possible exception is, as such, nobler than the other kinds; still, it is not always stronger in a given case; thus, I am more intensely convinced of Caesar's death, which is a matter of moral certainty, than of many theses in Mathematics or Philosophy, which rest on metaphysical principles.