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Chapter 2

The Solution To The First Question:
'What Must I Do When I Am Uncertain Of The Lawfulness Of My Action?'

471. When the first question has been reduced to these simple terms it is answered easily and without controversy. St. Alphonsus says clearly: 'It is never lawful to act with a practically doubtful conscience,' (as theologians commonly call the state of uncertainty we have described). 'If a person does act in this case, he sins. The gravity of the sin corresponds to the species and gravity of the sin about which he doubts.' St. Alphonsus gives the reason: 'If someone exposes himself to the danger of sinning, he already sins, as scripture says: "Whoever loves danger will perish by it." (327) If therefore he doubts whether the sin is mortal he sins mortally.'(328) He concludes: 'If a person has a practical doubt about an action, he must certainly first remove the doubt through some certain or reflective principle assuring him of the morality of that action.'(329) No Catholic theologian disputes this.(330) We therefore take it as an undoubted source of light from which to continue our study. It only remains to explain it and draw the necessary conclusions.

472. We begin by reaffirming that we can posit an act lawfully only if its morality or lawfulness is certain for us; it is not sufficient for its lawfulness or uprightness to be probable. We have to avoid every willed danger of sin. If any little doubt remains about sin in our act, we willingly expose ourselves to the danger of offending against the law. Our spirit can never rightly intend this, and should flee from it absolutely.

473. This conclusion, however, has nothing to do with the question of probable opinion which is not connected with practical doubt but with what theologians call speculative doubt. Practical doubt is concerned with the final dictate arising from the application of probable opinion to the particular act that we wish to perform. The proposition condemned by Alexander VIII: 'It is not lawful to follow even the most probable of probable opinions', is not applicable in the least, therefore, to the general teaching of theologians which states: 'To do something sinlessly, it is not enough to hold that the action's lawfulness is highly probable; we must be certain that it is lawful.' In other words, we must be certain that our act does not offend God.

This unshakeable, universal teaching common to Catholic moralists cannot be expressed in all its clarity unless we begin by defining what we mean by the word certain, and by understanding how the certainty of which we are speaking differs from probability. What, therefore, is certainty?

474. We have defined certainty as 'a firm and reasonable persuasion that conforms to the truth.'(331) As a persuasion, certainty is a state of the spirit. We have defined persuasion as 'our understanding resting in the assent we give to a proposition.'(332) But the assent in which our understanding rests, if it is to constitute certainty (as the definition of certainty affirms) must be reasonable. This means that assent must be generated according to reason.(333)

475. The reasonable motives producing a state of certainty in our spirit can vary. As a result, different kinds of certainty can be distinguished.
First, I have already noted two general kinds of certainty. One of them is generated when we see the necessity of the proposition to which we assent simply as part of the proposition itself. For example, I say: 'I am certain that at every instant a body must either move or be still.' I have no need to appeal to anything extraneous to the proposition in order to see its necessity. As soon as the proposition is present to my spirit, I see its necessity, the foundation of its certainty.(334)
The other kind of certainty is founded in certainty about a fact. In this case, the proposition is not itself necessary, but depends on a contingent fact for its necessity. For example, the proposition 'I am moving' contains nothing necessary, but expresses a fact which, if granted, makes the proposition certain.
These two supreme kinds of certainty can be called logical and physical certainty. The former is contained in ideal being; the latter consists in the relationship of equality between ideal and real being.

476. We can also distinguish a third kind of certainty which depends on authority. We shall call it didactic certainty.

The first two kinds of certainty are distinguished from one another by the objects with which their certainty is concerned. These are either ideal and necessary objects, or contingent-real objects made known and certain through their relationship with ideal objects. The third kind of certainty, however, is not distinguished from the others by the nature of its objects, but simply by the channel which transmits the certainty to us. By means of authority we can obtain certainty about both purely ideal objects and mixed objects provided that what another teaches us is not simply a stimulus to our own thought on the matter but a communication of their own certainty. In this case, the teacher or witness does no more than communicate his own certain knowledge of things. In so far as his act communicates knowledge it is called teaching; in so far as it communicates certainty, especially certainty about facts, it is properly called witnessing. Hence, didactic certainty is always reduced to one of the first two kinds of certainty according to the quality of its objects (whether these are ideal, or real as well as ideal) and only adds a new means of communicating.

477. This means of communication is itself a fact. From this point of view didactic certainty is reduced to physical certainty, or rather needs physical certainty as its condition and support.

478. Because of this diversity of its general objects, didactic certainty differs from the other two kinds of certainty. Hence we have: 1. certainty proper to ideal or necessary objects; 2. certainty proper to contingent-real objects; 3. certainty extending both to ideal and to real objects.

479. Just as didactic certainty is reduced to physical certainty from one point of view, so physical certainty is reduced to logical certainty. Certainty about facts (the object of physical certainty) is founded on a preceding logical principle, as I have shown.(335) For example, the certainty of the proposition 'I am moving' springs from the principle: 'Given the fact of intellectual perception of movement, movement itself is undeniable because it forms an element of that fact. If my movement could not exist at the moment I perceive it, it would be, and not be, at the same time. Through the fact of perception, therefore, a proposition which of itself is contingent becomes necessary and is reduced to a particular case of the principle of contradiction.'(336)

480. This argument, in which the certainty of movement is deduced from the purely logical principle of contradiction, is undeniable provided only that the fact of movement is an element in the perception of the movement (I have shown at length that this is so), and provided that the fact of perception is certain. But the certainty of the perception, although pertaining to the order of real things, is rooted in ideal being, the seat of logical certainty, because what is perceived intellectively is perceived in ideal being as in its term or end whose truth it thus shares.

481. Didactic certainty is reduced therefore to physical certainty, and physical certainty to logical certainty. Nevertheless, these three kinds of certainty have to be distinguished: logical certainty, which bestows its own evidence on physical certainty, does not always and necessarily contain the physical fact to which it communicates certainty, nor is physical certainty always and necessarily received on the authority of another.

482. We can now subdivide into species the three supreme genera of certainty.
Physical certainty can primarily be divided into conditioned and unconditioned certainty or, to we use Greek terms, apodictic and hypothetical certainty. Apodictic certainty is absolute, hypothetical certainty is conditional, and because it depends upon a condition, can exist only when its condition is certain. For example, if a physical cause really subsists, some real effect must follow; but the effect is certain only on condition that the cause subsists. Certainty is present, therefore, only if the condition has been realised.

483. We may note here that many authors who seem to admit some kind of hypothetical certainty even in the simple order of ideas, are misled by their own way of speaking. They say: 'If there is a human being, this person must have a body and soul', and go on to conclude that the proposition, which expresses simple possibility alone, is conditioned. But the notion of human being necessarily includes, without any exception whatsoever, body and soul. Hence we necessarily think of a possible body and possible soul in the human being, without any condition. Consequently we do not need to posit the conditional phrase: 'If there is a human being'; a possible human being must necessarily be possible, and cannot not be. On the other hand, in saying: 'If there is a human being, this person must have a body and soul' we simply affirm: 'If there is a human being, there must be a human being.' The body and soul in question are precisely the human being. Hence, 'human being' is not a necessary condition for 'body-and-soul-being' - it is the same as 'body-and-soul-being'. Purely logical certainty, therefore, contains nothing hypothetical although, granted human limitation, one thing always precedes another relative to us.

484. Finally we must add that our limited mode of understanding explains why we introduce suppositions or hypotheses in the order of logical truths, although these suppositions or hypotheses are often simple absurdities. For example, given an absurd supposition, we draw absurd consequences which seem to possess hypothetical truth, that is, truth conditioned by the initial absurdity. In fact, because the initial supposition was absurd, the consequences possess neither truth nor certainty. It is clear that on this basis there is no authority for affirming the presence of hypothetical certainty in the order of purely logical truths.
We can, therefore, disregard all ideal, hypothetical certainty because it lacks all the characteristics of certainty, and hence cannot be called certainty in the strict, absolute sense. We shall confine our attention to apodictic, demonstrative, unconditioned certainty.

485. What are the specific divisions of logical certainty, physical certainty and didactic certainty?

Logical certainty is divided into intuitive and rational. Intuitive certainty, as I understand it, is that certainty in which I see immediately the necessity of ideal being. Logical-rational certainty, again as I understand it, is that by which I deduce many truths through analysis of, and by reasoning from, the intuition of possible being and the perception of necessary real, or moral facts. That is, I see these truths one within another, and finally behold them together, contained in the splendour of first being. Logical-rational certainty is derived, therefore, from intuitive certainty, its source and first seat. Consequently, logical-rational certainty is divided into the certainty of ideas and the certainty of necessary real, or moral facts.

486. The species, 'physical certainty', that is, certainty relative to subsistent things, is also twofold: perceptive certainty and physical-rational certainty. Perceptive certainty is proper to intellective perception. This certainty does not differ in grade from logical, intuitive certainty; it differs only in so far as its object does not contain in itself any intrinsic necessity. Physical-rational certainty is deduced from perceptive certainty by means of right reasoning.

487. Perceptive certainty is divided also into two classes according to its objects. In our present state we have two objects of intellective perception: 1. corporeal feeling (extrasubjective) and 2. feeling of ourselves (subjective). The first of these feelings provides our understanding with the matter required in the perception of bodies; the second provides our understanding with the matter required for its self-perception. These two classes of certainty can therefore be called esthetic and psychic certainty.

488. At this point we may ask whether any certainty is founded on the law of analogy and, if so, to which of the above-mentioned genera it belongs.
It is clear that analogical certainty, if it exists, can never belong to the genus 'logical certainty' but only to physical or didactic certainty. Analogy is never used for argument in the order of ideas, where the sole basis of reasoning is the necessity connecting the ideas.

489. But does analogical certainty exist? This can be decided only on knowledge of the law of analogy and of the principle on which this law depends. We must therefore examine the nature and principle of analogy.
The law of analogy embraces time and space.

When something has occurred frequently and periodically we judge that it will take place again when the same interval has elapsed. For example, we judge that the sun will rise tomorrow because it always has risen at daily intervals. From analogy with the past, we judge what will happen in the future.
What we say of time can also be said of space. A Tyrolese peasant who has spent his whole life in some remote mountain valley will be very surprised at what he sees when he has to go out into the world at large. His surprise springs from reasoning according to the law of analogy: accustomed only to what he has known in his own isolated community, he reasons that the rest of the world lives in the same way.

490. The law of analogy includes substances and accidents and, in general, every connection between things. When I hear a voice calling my name, although I see no one, I reason by analogy that there must be someone unseen near by. Experience has taught me that every time I hear a word articulated, a person must be present to pronounce it. Nevertheless, I may be deceived; perhaps a parrot has been taught to pronounce my name.

491. The law of analogy leads us therefore either from an effect to a cause, or from a cause to an effect, or from a sign to what is signified, or from one property to another experienced as normally connected with it.

492. But what is the final foundation for this law of analogy, which we use so often, on which we continually base our reasoning, and without which it would perhaps be impossible to live? This question is twofold: either we are asking about the nature of the principle within us which moves us to rely so confidently on this form of argument, or we are asking about the foundation of analogy in nature which leads us in fact to make few mistakes when our reasoning depends upon analogy.

493. In answering the first question we begin by recalling that we are reasonable beings. Clearly, therefore, we rely on analogy largely because a principle of reason persuades us to do so. This reason may be hidden within us and not reflected upon, but it must nevertheless be intuited by us in the depth of our spirit where we behold many things unexpressed even to ourselves. This principle of reason must also provide the explanation for our making few mistakes when we argue from analogy. The answer to the second question, therefore, contains at least in part the answer to the first. I say 'at least in part' because reasoning from analogy must depend not only upon a principle of reason, but also upon our being moved by an habitual principle which accustoms us to reason at least formally in a consistent fashion.(337)

494. But this need detain us no longer. We now have to seek the reason which, rooted in the nature of things, enables us to avoid frequent mistakes in our use of analogy. This reason provides us with the secret assurance that our way of arguing by analogy is sound. It may be stated as follows: 'The value of analogy is based on the constancy proper to substances, things and the properties of things.'

For example, when we see an effect reproduced every twenty-four hours, we begin to be persuaded that there is in nature a suitable cause for producing that effect every twenty-four hours. It is clear therefore that the concept of cause involves the concept of constancy, just as it does the concept of substance. We conclude, therefore, that the periodic effect will continue in the future as it has in the past because we are certain that its cause, which of its nature is firm and consistent relative to the effect, will continue to exist. For the same reason, we presume that the order of the universe will always be stable. This order is the result of a complex of effects that depend upon substances which, as permanent causes, produce transitory effects that either occur periodically or are renewed according to certain laws proper to the nature of these substances.

495. We must note, however, that the argument from analogy should not be confused with that of cause and effect, although both are founded on the principle of cause as follows.

If we can prove that a cause subsists at the present moment, we can certainly conclude as a direct consequence that all the effects necessarily springing from it also exist. This is the argument from cause and effect, not from analogy; it is self-evident and leads to full certainty.
On the other hand, it may be that we cannot prove the existence of a cause at the present moment. We know only of its previous existence through the effects, seen by us, which it constantly produced. We argue from this knowledge that the cause still exists, that it will exist tomorrow, and that its effects will come about. Granted the stability of the cause as a substance, or as rooted in a substance, we argue from the past existence of the cause to its present and future existence.

496. If however we are dealing with a contingent cause, it would not be absurd for a substance which has existed at length in the past to cease to exist in the future, through annihilation or destruction. The same can be said about any special power in the substance which makes the substance cause the observed effects. The cause would cease if this particular power ceased, although the substance in which it existed might continue.
The argument from cause and effect, therefore, always produces certainty because the existence of the cause is proved in the instant in which the effect is produced.

On the other hand, the argument from analogy is not always certain because the existence of the cause is not proved, but presupposed in the argument. The cause is conjectured in virtue of its constant existence as a substance. In this way we affirm tomorrow's sunrise as a consequence of the implicit supposition that the substance of the sun continues to endure with the same laws with which it has lasted until now. This supposition is not proved, however, but only conjectured from the principle of duration of order in the universe, which itself is founded on the duration of the substances composing the universe.

The argument from analogy is not such, therefore, that it can, of its own nature, bring about certainty. At most, it can offer probability which, although it may be very strong, can never compel free assent.

497. Moreover, just as the strongest probability can be induced by analogy, in some cases the probability can be weak or nil. This occurs when our argument arbitrarily presupposes a non-existent stability of order, as we have seen in our example of our Tyrolese peasant. Supposing that everyone dresses in Tyrolese costume, our peasant may think he will find the same dress everywhere he goes. But the only foundation for this constant, universal supposition is his own limited perception of what people wear. In his case, the argument from analogy fails.

498. Analogy has to be used cautiously, in accordance with the qualifications provided by sound logic. If it is employed in this way our conclusions have some probability, which may vary from very weak to very strong. When probability is at its strongest, it may even possess enough force to capture the assent of our spirit, and only with difficulty be distinguished from certainty. Nevertheless, it never passes the bounds of probability; it is not certainty.

499. We must now examine the species composing what we have called didactic certainty.

500. As I said, didactic certainty is reduced to physical certainty (cf. 471) because the teaching or witness of others is normally received through perception (the seat of physical certainty). However, we have to distinguish in this species of certainty absolute didactic certainty and normal didactic certainty.

501. Didactic certainty is absolute when its teacher or witness is infallible, especially if the master or witness has the power (and this is the case with God) to enable his hearer, into whom he infuses evidence and persuasion, to receive with conviction what is communicated.

502. Didactic certainty is normal only when the authority of the master or witness is such that the moral law authorises us to take this authority as a norm for acting. This occurs, for example, in the case of direction from a confessor or religious superior, or in the case of belief about factual matters when we depend for our knowledge upon persons worthy of credence.

503. This kind of normal certainty presupposes that the person communicating it is himself in possession of it. If his knowledge were only probable, not certain, he could communicate his probability, but not the certainty which he lacks.
How then does a human being come to possess certainty? If it has been communicated to him by his own teacher, how does that teacher come to possess it? The problem must eventually be grounded in the first person to possess certainty, which will have been acquired not on the basis of teaching or witness but through logical or physical means (according to the kind of certainty possessed). Physical means enable a person to acquire physical certainty, which always refers to some subsistent being or to some fact, on condition that he is willing to use 'fact' as synonymous with 'subsistent.' Logical means enable him to acquire logical certainty. Didactic certainty, therefore, must ultimately be subdivided into physical and logical certainty.

504. Generally speaking, if we come to know facts through didactic certainty, we possess historical certainty; if we come to know various rational teachings in the same way, we possess doctrinal or dogmatic certainty.(338)

505. For a witness of facts to be authoritative, there must be no exception which allows reasonable doubt about the certainty of what he says, or about his willingness and capacity for communicating the certainty. If no exception is present, any person must be considered a suitable channel for communicating certainty.

506. In order to communicate doctrinal certainty, however, a teacher must not only possess it himself, but also show certain proof that he possesses it. More is required of a teacher than of a witness, as a channel of certainty. Although every human being must be presumed truthful when there is no reasonable doubt to the contrary, not everyone can be presumed learned. Positive proof of his teaching is needed if others are to believe in his learning.

507. However, when counsel is needed on moral matters, the teaching of a churchman is sufficiently proven if he is universally respected for his wisdom and above all for his uprightness which will prevent his giving moral advice with complete certainty if he himself is not certain of what he teaches. His uprightness is a proof of his truthfulness, and his truthfulness is evidence that he possesses sufficient sound doctrine to give advice when he is asked.

508. If a witness to a fact is open to exception, his statements can induce probability only. If other witnesses concur with him but themselves are open to exception, the conclusion can only be more probable, but never certain until at least one witness is found who is completely sound and consequently worthy of credence. Agreement on the part of witnesses who are not altogether worthy of credence gives rise only to a calculation of probability.

509. The same must be said about knowledge of any fact communicated by a series of intermediate witnesses. If an immediate witness is worthy of credence, his word alone gives rise to certainty, provided his testimony has been securely documented. If the first testimony has been lost, certainty can arise in the case of a mediate witness only when he himself and those from whom he has received the testimony and the documents containing it are all proved worthy of credence. In such cases, the means by which we attain certainty are the witnesses taken in conjunction with reasoning. This is critical certainty, which itself is subdivided into historical or perceptive-historical certainty, and rational-historical certainty.

510. The schema on the following page will help summarize what we have said about the different species of certainty.

Schema of Certainty - (Image) 

511. What we have said allows us to differentiate certainty and probability.
Although we have various means for reaching certainty, in each case we have finally to arrive at intuitive, logical certainty based upon principles possessing evident, immutable necessity, the only solid foundation of every certainty.

Probability, on the contrary, is present when our reasoning cannot be brought to terminate in any evident, per se necessary principle but has to rest in a law or principle from which necessity cannot be induced. The law of analogy, which we have already examined, is one example. The affirmation 'This has gone on for a long time, therefore it will continue' is not a necessary principle, and hence not universally applicable for all times and places. In order to possess a necessary, universal principle, it is not sufficient to know what has gone on for a long time. We must also know the cause producing or renewing the effect over such a period. In fact, we do not know this cause; we induce its constancy only from the constancy of the effect. But the effect itself tells us only that the constancy of the cause has been sufficient to bring about the effect until the present moment; it does not tell us in any way that its nature will be sufficient to make the effect last. This we conjecture. When we argue from analogy, therefore, the argument proceeds from cause to effect, but does not induce certainty because our knowledge of the cause is incomplete and defective. Our conclusion possesses only the grade of certainty present in the knowledge of the cause from which we induce the conclusion.

512. Examination of another kind of argument producing probable conclusions will help us understand better the difference between arguments terminating in certainty and those terminating in probability.

Imagine a bag containing ninety marbles, ten red and eighty yellow. The probability of my extracting a yellow marble is obvious, but this is not certainty: I could take out a red marble. In foreseeing that I will take out a yellow marble, I depend upon probability, not certainty, for the simple reason that we lack full, perfect knowledge of the cause of what is happening. If I knew all the circumstances present in determining the extraction of the marble, I could foresee with certainty the colour which would emerge. If, for instance, all the marbles were yellow, I could be sure that whenever I put my hand in the bag, a yellow marble would be extracted. The effect is determined by the colour of the marbles which, in this case, are all yellow. In the case of different coloured marbles, my hand is not predetermined to a single colour. I mean that it is not determined as far as I am concerned, as far as my knowledge is concerned. In fact (leaving aside the question of free will) it is always determined by definite, hidden causes and reasons, but these are unknown to me. I do not know the efficacious, physical causes determining the action of my hand, nor do I know the relationship of these causes with the colour of the marbles. I am forced to reason simply on the basis of data known to me. In the present case, this means that I am limited to arguing to the determining cause (that is, the movements of my hand) from the proportion of yellow to red marbles. And this is insufficient for providing me with full information of the cause determining me to extract the particular marble that emerges from the bag.

513. On the same basis we can see why agreement between witnesses all of whom are open to exception can induce probability only, never certainty, whatever the number of the available witnesses. Although I am aware of the agreement present in the various depositions, I also know that I can be fully certain of what is said only if each of the depositions has a single cause, that is, the truth. In such a case, I can with full certainty induce from the effect, that is, the agreement between the witnesses, the truth of their depositions. But if their agreement can be produced by a cause different from the truth of their deposition, this possible cause is sufficient to show that I may not fully know the cause or the complex of causes which induced the witnesses to give common testimony. This defective knowledge of the total cause means that I can never reach full certainty about the matter, but only probability which is greater in so far as the deficiencies in my knowledge of the cause are smaller.

514. What I have said about the different kinds of certainty may have led my readers to think I have broadened the field of certainty more than is necessary. Such an objection could be stated as follows.

It is agreed that there are truths given by nature about which we cannot fall into error. This is easily grasped on the basis of what has been shown in The Origin of Thought.(339) It is also clear that everything deduced by right reasoning from the first truths, or reduced to the first truths as principles, is immune from error. But how can we be sure that we have reasoned correctly? Granted our fallibility, is it not possible for us to err even in the first deductions we make from the sensations we have received. For example, we sometimes judge that a body is moving, although it is in fact motionless, and are led to make this mistake by the appearance of movement arising from the spatial relationship of the body with others that are moving. We must conclude, it would seem, that we can have certainty only about the small sphere of truths in which nature protects us from error. In other cases, we possess only various degrees of probability.

515. This difficulty, although it has a basis of truth, is false if taken too far, as it has been in modern times.(340)
First, the human spirit can sometimes be found in a state in which the truth of certain consequences is clearly grounded in principles, with the result that our persuasion is felt to be as free from error as it is in the intuition of the very first truths.

516. Second, we have to distinguish certainty which excludes the possibility of error from certainty which excludes error but not its abstract possibility. The second kind, although it does not totally eliminate all abstract possibility of error, is certainty no less than the first kind because 1. the means bringing it about are per se infallible; 2. the possibility of error arises from the general knowledge of our fallibility without any particular reason causing us to doubt the certainty we possess.

If it is considered desirable to grade the simple, general possibility of error and fallibility I would be happy to distinguish rigorous from normal certainty. The former would be certainty related to matters about which nature protects us from all error; the latter, certainty about things we come to know through per se infallible means, although the mere general possibility that we may have erred in using them still remains. It is always true that this normal certainty is sufficient to allow us to act decisively without any reasonable fear of damage or sin, and for this reason it is called moral certainty. It is also true, and this must be noted carefully, that it has to be distinguished from even the highest probability.

517. What we call normal certainty differs from probability in so far as it is attained with means that are per se infallible; probability, on the contrary, depends upon the use of means that are not per se infallible.

518. Any doubt remaining in conjunction with normal certainty is negative doubt. It offers no particular reason for fear of error except the universal possibility we have of erring in the use of the means producing certainty, even when we do not appear to have made any mistake whatever. In probability, however, a positive doubt is present, that is, a special reason for fearing that our conclusion may be mistaken.

519. Fr. Valperga di Caluso puts the matter very well, and we may use his authority to confirm our own observations. He says: 'We must not confuse the issue. We can ask if there are truths that must be known and if there are mistakes so gross that neither erroneous reasoning nor madness can attain them. But this is not in question here. We are not trying to restrict the matter to a small number of incontrovertible principles (such as existence for the individual, or the universal principle that a thing is unable to be and not to be at the same time). We are speaking about certainty in contested matters. If certainty has to be present where facts all too often prove our fallibility, certainty can scarcely be infallible.

'The adjective doubtful must add something to its noun, but would signify nothing if it indicated only the simple possibility of doubt. Careful attention to the way we speak will show that something is said to be doubtful only when a particular reason for doubt is applicable to the case. The reason may not have much weight, but it will be specifically applicable to the case in question. It is true that we can doubt about everything, and that our fallibility is an ever-present reason, good or bad, for this doubt. But our question' (how to know whether something is doubtful) 'is not concerned with this doubt. When we say that something is doubtful, we never think about this general reason which is foreign to what we are talking about, and completely absent from our minds and intention. The reason for universal doubt, that is, our fallibility, is present in us; the reason for saying that one thing is doubtful rather than another must be found in the thing itself. Something will be doubtful if there is a particular reason for doubt; it will be certain if no particular doubt is present in its regard.'

Shortly after he adds: 'The attention we should give to this reason for doubt, in so far as it is applied to particular cases, is altogether different from the knowledge that we have about our fallibility in general. In the first case we are concerned with reflective knowledge which, springing from an exact, detailed examination of a question which we consider from all sides, can indeed provide us with unassailable, if not infallible, certainty. Sometimes our sensation of certainty is so vivid, our memory of it so firm and positive, and our reasoning so clear and conclusive, that we could not doubt even if we wished to.

'However, only direct doubt is impossible when we examine a question in itself. But an indirect doubt, extraneous to the question, cannot be in contradiction with the evidence offered by the question, precisely because the doubt is indirect and irrelevant. We often say: "As certain as two and two are four", and all arithmetic is equally certain to those who know it. But at the end of a long calculation, carried out and verified with all possible attention, we write errors excepted.'(341)

520. A further answer is required, however, if the difficulty we have broached is to be entirely overcome. First, we have to reflect on the great difference between the direct and indirect doubt referred to by Caluso.
Indirect doubt rises from our reflection on the solution to a question; direct doubt arises within the question itself. But if the solution to the question is examined on all sides, and no foundation is found for doubting the correctness of the solution, the indirect doubt must be considered an idle fear rather than a true doubt.

521. It is certain that while human beings are in the first stages of their development and do not exceed first-level reflection, they think and act with conviction, free of any disturbance whatsoever from indirect doubt. Either they see what is true and enjoy it, or they do not see it and they remain ignorant, but without any doubt.

522. When, however, the mind rises to higher levels of reflection, indirect doubt is stimulated, that is, fear of having erred even in those acts in which no error exists. This indirect doubt or fear cannot provide sufficient reason for causing us to lose the completely firm certainty we previously possessed.

523. Nevertheless, we can see more clearly how practical, normal certainty has as much claim as rigorous certainty to the title certainty if we ponder once more our definition of certainty: 'a firm and reasonable persuasion that conforms to the truth.'
This definition shows that true certainty can be present in a great deal of knowledge not protected from error by nature. Even here it can and does happen that we 'assent firmly and reasonably' precisely because we assent as a consequence of using per se infallible means of certainty, and that 'our assent conforms to the truth.' Given this assent, all the conditions necessary for constituting certainty are present within us.

524. It may be objected that we are not infallible, and that our assent can therefore be deceptive. That is true, but the possibility of deception does not destroy certainty, provided we are not in fact deceived. Saying that we can be deceived is equivalent to saying that we are able not to be certain. But if in fact we are certain, being able not to be certain expresses nothing. What is in question is whether we possess certainty or not, not whether it is possible to possess it or not. Whoever we are, we possess certainty in fact when, using one of the means of certainty which we have called 'infallible', we give our assent simply and firmly. Simple, upright people always do this, especially if, as we suggested, they have not attained high-level reflection.

525. We exaggerate if we allow the possibility of human self-deception to affect us in such a way that we become restless and lose the quiet and peace of truth as it offers itself to our gaze. In such a state, assent to truth begins to vacillate. This kind of exaggeration and idle fear paves the way to scepticism for many.
We are made for truth; we possess and use per se infallible means for knowing the truth. All that remains is that, whenever we are in possession of these means, we adhere to them simply and tranquilly without cavilling: then certainty is formed. 'But one can deceive oneself!' Yes, we can deceive ourselves in general, but in very many cases we do not do so, and here lies certainty. We can deceive ourselves, but only when we let ourselves be overly dominated by fear of deceiving ourselves. It is this fear which removes the the firmness of assent that we must give and would give to the truth standing before us if we were not afraid. We can deceive ourselves, but only when, instead of giving our assent to the means of certainty we possess, we willingly create errors, or confuse the means providing probability with those offering us full certainty.(342)

526. Our final reflection enables us to overcome the difficulty entirely. We have already distinguished willed from unwilled error, and we saw the almost unlimited field open to the efficacy of our will in generating error.(343) We noticed that we cannot deceive ourselves through formal error if we have an upright will. In such a case we can only fall into material error, which is not error, properly speaking. Human fallibility, so exaggerated by sceptics and abusively turned to their own advantage, proves on careful examination to be simply the fallibility of the human will. If, therefore, we are in possession of an upright will, which is without love of any sort for error or for self, but full of love for naked truth, we will easily reach certainty - just as, if we want to be virtuous, we will attain virtue. And as the power we have of making ourselves virtuous does not remove our possibility of being vicious, if that is what we want, so having certainty within our grasp does not render us infallible in such a way that we cannot deceive ourselves, if that is what we want. In a word, we can deceive ourselves because we are able to love something other than truth. Disorder can gain entrance to our affections, but only on condition that our will consents to its entry. Without the deleterious action of our will, our powers are upright, and each of them in relationship to its object is infallible.

527. Drawing together all that we have said about certainty in our endeavour to clarify the moral rule we have set out, we may conclude as follows.
If we are intimately persuaded of our certainty about the lawfulness of an action, and this persuasion is not an error dependent upon our evil affections, we can safely act. But if we are doubtful that an action is lawful, although its lawfulness may seem probable to us, we cannot act until we are sure that it is lawful. We note, however, that the degree of doubt telling us that we are less than fully certain of the lawfulness of our action is something more than the simple, general thought of human fallibility, which is not sufficient to make any judgment of ours uncertain. Nor is it simple fear devoid of rational motives. Such fear is powerless to weaken our certainty and diminish the rational assent in the depths of our spirit unless the assent of our will moves the faculty of judgment to act according to the fear. We saw that this often happens with scrupulous people.

528. If a person gives way to irrational fear (and this usually occurs when a state of nerves takes hold of the person at the mere thought of the possibility of evil which through his overheated imagination he has changed into probability) and changes shadow into solid body, he adds another judgment and persuades himself of fault where none exists and, as we saw, develops the scrupulous conscience that must be eliminated before he acts.

529. We cannot act without sin if we are uncertain about the lawfulness or unlawfulness of our action. But what is the nature of the sin we commit?

Its species is determined by the quality of the action, considered from the moral point of view; its gravity and malice is calculated relative to the degree of probability of its unlawfulness as understood and assented to by us - although other circumstances may also have to be considered. First, it is certain that in positing an action which we certainly know to be unlawful we sin more seriously than in doing something which we know to be doubtfully unlawful. In the same way, it is clear that the higher our degree of probability about the unlawfulness of an action, the greater our sin when we do it, and vice-versa. If therefore the probable degree of unlawfulness is slight, our sin will be slight (although truly sin).

530. If the degree of probability is so slight that we fail to consider it, and give full assent to the lawfulness of the action as though it were undoubtedly certain, we commit a venial sin of lack of attention and nothing more.

Notes

(326) The same must be said of an omission if our doubt concerns a precept commanding some action.

(327) Sir 3: 27 [26].

(328) Liguori, De Consc., c. 2, n. 22 [App. no. 5].

(329) Liguori, De Consc., c. 2, n. 24.

(330) Fogarini in his Tractatus Theologicus de certitudine honestatis in actibus humanis (part 1, p. 8) lists certain authors who maintain that it is lawful to act 'while fearful of possible malice in an action to be carried out immediately.' But Father Steidel, from the district of Trent, says that these authors 'differ only verbally from the very general teaching about the necessity of moral certainty relative to the morality of an action.'

(331) Certainty, 1044.

(332) Certainty, 1336.

(333) Certainty, 1052-1053.

(334) The certainty of necessary facts can be reduced to logical certainty: I can know their certainty only if I know their necessity. But knowledge of their necessity is always reduced to the intuition of a necessary proposition.

(335) Certainty, 1342-1345.

(336) Certainty, 1342-1345.

(337) One general principle governing instinctive human behaviour is: 'From all the actions in which activity can be expressed, the human being always chooses for himself the one which causes the least fatigue,' that is, the easiest - other things being equal.

(338) We may first believe a teaching on the authority of another, but then go on to understand the reasons for the teaching. But if the reasons persuade us that the teaching is true, we can be said to possess doctrinal teaching (in so far as we believe the teaching on authority) and logical teaching (in so far as through logical argument we reach certainty about the teaching).

(339) Certainty, 1061.

(340) Lamennais' troubles began in this way.

(341) Principes de Philosophie pour des initiés aux mathématiques, by M. Valperga di Caluso, member of the Légion d'honneur, etc. Turin 1811. Au palais de l'Académie, by Vincent Bianco.

(342) This is why St. Augustine does not hesitate to say that there is no error in what the intellect sees: 'But he (the human being) does not err in what is seen by his intellect: either he understands, and it is true; or if it is not true, he does not understand. It is one thing to err in what he sees; it is another to err because he does not see' (De Genesis ad litt., bk. 12, c. 25, 52).

(343) Certainty, 1245.