Jacques Maritain Center : The First Principles of Knowledge

Chapter XIV.
The Origin of Error in the Understanding.


  1. Ignorance the root of error. How we begin in ignorance, slowly acquire some knowledge, but never cease to be in many ways ignorant.
  2. The scholastic theory about error is, that the intellect is per se infallible, per accidens fallible: and that undue influence of the will is exerted in the case of error.
  3. The scholastic theory taught outside scholasticism.
  4. Supplementary considerations to complete the theory. (a) Dependence of the intellect on organic conditions, which are liable to disturbance. (b) The force of habit on the interpretation of sensation by the intellect. (c) The piecemeal, defective way in which we obtain evidence.
  5. The scholastic theory re-stated and modified by the supplementary remarks.


THE next problem pressing for solution is to settle how, in spite of the fact that in evidence we possess an unerring criterion, yet we do err: so that intellectually, perhaps as much as morally, humanum est errare. The difficulty weighs heavier upon us than it would on those who, with Grote, believe that "no infallible objective mark, no common measure, no canon of evidence recognised by all, has yet been found." We who assert such a canon, have to explain how intellectual error is not only possible, but of constant occurrence, being sometimes practically inevitable.

I. Ignorance is not itself error; but it lies at the root of error; inasmuch as, while an Omniscient Being cannot err because of His omniscience, a creature, because his knowledge is but partial, is exposed to the risk of forming false judgments. It is the little knowledge that is the dangerous thing.{1}

We must, then, advert to the fact of our ignorance -- how we begin in blank ignorance, very slowly emerge from the universal darkness, and never reach the full blaze of knowledge complete. Our knowledge is always a small sphere of illumination enclosed in an infinite sphere of obscurity; and the more the former grows, the more does its wider contact with what is without make it sensible of its own limitations. Consider our personal history. For years the brain is not fit to serve the uses of higher intelligence: and when what is called the age of reason has arrived, long years of education are still needed to form the faculties into efficient working powers. Again, when at the age of about twenty the condition of pupilage is over, a young man is told, as a parting piece of advice, that he is not a learned Doctor, but that he has the outfit necessary for setting about the work of becoming learned; and that even in its fully developed state, human learning is an ornament which is to be worn with a modest appreciation of its perfection. Moreover, the knowledge which a man is said to have acquired is not always ready at need, as a schoolboy doing his Latin exercises will testify: and the knowledge that does not come up when wanted, is for the moment equivalently ignorance. Such is the extent of our ignorance.

2. Ignorance being supposed, the transition from it to error has to be studied: and in the course of our explanation we shall come across the promised account of how it is, that while judgment is defined as the full perception of the connexion between subject and predicate, yet judgments may be false.{2} It is the theory of the scholastics that intellect in man is per se infallible, per accidens fallible; or more accurately, per se non fallitur, per accidens fallitur. For it is per se fallible only inasmuch as, being per se a finite intelligence, it is of its own nature exposed to the possibility of going astray, but it does not simply of its own nature actually go astray. Similarly the finite will is per se peccable in so far as it is exposed to the possibility of sinning, not because per se it sins. The intellect, as such, is moved only by its own proper object, which is evidence; and as evidence is the unfailing criterion of truth, the action of the intellect, strictly so called, is never erroneous. Intellect acting per se goes only by insight, and insight is always right. Thus insight per se can no more assent to anything but truth, than the ear proper can be sensible to anything but sound. But intellect, so far as it is subject to the undue action of the will, may be moved to go beyond or against the evidence it has at its disposal. This theory will be defended as in substance correct, though it may be usefully supplemented with some further considerations, much urged by modern writers. First, however, it may gain for itself a little more attention, if it is shown not to be an exclusive property of scholasticism, but to be owned likewise by thinkers of various classes. A multiplicity of approvers may induce some not to pass over the theory in contempt.

3. Hamilton was fond of quoting the line from Manilius -- whom we may take as our oldest witness, returning after a moment to Hamilton himself -- Nam neque decipitur ration, nec decipit unquam. Second in order we will take Descartes, who assuredly had no scruple in breaking loose from the scholastic bonds of his early educators, whenever it suited him. He holds firmly to the doctrine that error springs from the bad use of the will, not from intellect left to itself. In the first book of the Principia he writes:{3} "That we fall into error comes from defect, not in our nature as such, but in the employment of our powers, or in the use of our free-will. Since then we are aware that all our errors may be traced to the will, it may seem wonderful that we should ever be deceived, for nobody wishes to be deceived." Then he adds acutely: "But the will to be deceived is quite other than the will to assent to something which happens to involve error. And though it be true that no one is willing to be deceived, there is hardly any one who does not will assent to what contains error, though he be not aware of it."{4}

Another Frenchman,{5} Cousin, writes: "Pure error is impossible, and quite unintelligible: for error makes its way into the mind only by means of the truth which it contains."

Passing next to those who write in the English language, we may begin with the already promised quotation of Hamilton's opinion.{6} He holds that what we really and positively think cannot be erroneous, and that error is rather a want of intel. lectual action than an intellectual act. Mansel{7} concurs with his master, and holds that "illogical thinking is no thinking at all." Dr. M'Cosh'{8} is another consentient witness I cannot keep from giving it as my decided conviction, that while ignorance may arise from the finite nature of our faculties, and from a limited means of knowledge, positive error does, in every case, proceed directly or indirectly from a corrupted (?) will, leading us to pronounce a hasty judgment without evidence, or to seek partial evidence on the side to which our inclinations lean. A thoroughly pure and consistent will would, in my opinion, preserve us from all mistake." Finally, one who is not writing on philosophy shall join his voice to those of philosophers: "Mere sophisms or imperfect reasonings," says Mr. Lecky, "have a very small place in the history of human error; the intervention of the will has always been the chief cause of delusion."

4. This view that the will is the cause of error, supported as it is by so many authors, may be supplemented by some considerations much urged by modern writers -- considerations which are, however, really supplementary, not contradictory to the theory propounded.

(a) One source of delusion is in the derangement of the nervous apparatus; and the nature of this perturbing action will require some detailed account.

It is no new fact that a lesion in the material organ may result in stopping thought; and that on account of altered cerebral conditions a man maybe in any one of the countless gradations between sleep and wakefulness, or between sanity and insanity. And as sleep has its dreams and insanity its delusions, so in the intermediate stages just mentioned there may be intermediate degrees of deceptiveness due to an abnormal state of nerves, Some people labour under the frequent recurrence of visual or auditory illusions, which they can calmly correct by data supplied through the other senses. When the inflow of sensations from the ordinary channels is cut off, there are patients whose minds become quite deranged by their own subjective phantasies, and who are restored to composure only by being brought from darkness to light, and by having their several senses fed with their usual supplies. They need the steadying influx of impressions from the outer world to prevent the inner life from upsetting its own balance. An excitable man suddenly deprived of his hearing in a public thoroughfare, would often grow quite bewildered for want of his customary guidance from the ear: and still more would this be the case if the deprivation was effected, nbt merely through an external stopping of the ears, but through some inner disorder of the nerves. Thus in many ways a disturbance of the normal working of the nervous system has its result in a disturbance of the mind, and erroneous judgments not unfrequently follow.

From the most general statement of the fact we may now come down to a particular law, which may be enunciated thus: Whenever in the brain extraordinary causes which are internal excite those pbenomena which ordinarily are excited by familiarly known objects, there is a tendency erroneously to judge those objects to be present, though in reality they are not. Sometimes it is the vehemence of an idea which excites the sensible image, and at once the object is as if bodily present at other times the action is rather from below upwards, and the abnormally roused sense-images call up their corresponding ideas. Here we are safe in asserting that we have an undoubted occasion for an erroneous judgment, as for example when the vivid thought of a departed friend has brought up his image in the brain, and he is declared to have been seen. Some, though not all, ghost stories may be so explained.

(b) Again, there is a second special law of delusion through the senses, the law of the accidental miscarriage of customary interpretation; and it differs from the first in not implying any internal derangement of the nerves. Ordinarily, what we actually at any time perceive is the merest item, compared with all that is at once filled into the object by inference or association. We catch sight of a plume and we at once supply a hearse; we observe a wheel moving, and we supply the whole carriage and its occupants. An odour leads us to assert the presence of oranges or lemons; a sound the presence of an organist and his instrument; a touch a broken bone beneath its muscular covering. The practical necessities of life drive us to make these short cuts by the aid of incomplete inference; for if we stopped fully to verify everything, we could not get through one tithe of our business. As a rule, our customary inferences from few data are right, but every now and then they are wrong; and whoever cares to play us a practical joke may probably succeed in doing so, if under familiar appearances he will present to us an object not usually associated with them in our experience. In the examples given above, while we do not say that the unusually produced sensations or sense-images are errors, we must say that they may be occasions of error, and sometimes of error practically unavoidable.

This is the moderate statement of the case, and contrasts with the immoderate statement of M. Taine:{9} "The two principal processes employed by nature to produce what we call acts of cognition, are the creation of illusions within, and their rectification. It is a point of capital importance that external perception is a true hallucination. When sense-objects really impress us we have first the sensations, which an hallucinated person has without real objects. The external perception is an internal dream, which proves to be in harmony with outer things. We have, when awake, a series of hallucinations, which do not become developed. This hallucination which seems a monstrosity, is the very fabric of our mental life. Nature deceives to instruct us. In recollection a present image is taken for a past sensation. just as, in external perception, simple, internal phantasms are taken for external objects, so in memory we see simple present images taken for past sensations, but corresponding by a beautiful mechanism to the exterior presence of real sensations. The history of sleep and of madness gives us the key to the waking state." Mr. Sully{10} has some remarks of somewhat like tendency, when he is speaking of the region of hallucination as a border-land between reason and insanity, or rather as forming the extreme confines in which these two regions are, as it were, blended. He adds that "in perfect normal perception we find in the projection of our sensations of colour, sound, and the rest, into the environment or to the extremities of the organism, something which, from the point of view of physical science, easily wears the appearance of an ingredient of illusion." We may be pardoned, if in place of other answer to these authors we refer once more to the force which habit has in misleading us; for herein will be found the solution of the ordinary sense-illusions.{11} Those who reduce all judgments to repeated associations of ideas, naturally make much more of this source of error than we can allow; but we can allow that it is a source.

(c) Lastly, the criterion of evidence often fails to secure us from error, because we get our evidence piecemeal, in insufficient amount, and often with only indirect bearings. If the evidence of each case were one simple thing, we should run no risk; but, as was observed in the last chapter, we usually have to deal with a complicated mass of evidences in the plural.

5. Examining next how the scholastic theory can accommodate the three supplementary considerations, we note first that all three elements, at least indirectly, come under the control of will, to a large extent. By force of will we can often resist or correct abnormal conditions of the sensitive system, and by force of will we can aggravate these conditions. Again, will has a large share as well in forming our intellectual habits, as in checking them. Lastly, will has its influence in setting us carefully, cautiously, and restrainedly to judge from complicated evidences, or in urging us precipitately to force a conclusion.

While, however, these several conditions are controlled by will, they have distinct influences of their own; and this is the reason why the theory, that error is due to will, seems not complete, unless they too receive special mention as factors of the whole.

In what sense, therefore, from our larger survey of the position, can we admit Hamilton's dictum, that "No error can be really thought?"{12} Are we to say, that he who honestly mistakes his neighbour's hat for his own, does not really think it his own? Not so; but what we may assert is, that in his way of forming this judgment there were some steps taken in which thought was a blank. The man never really thought out all the steps to the conclusion -- "This hat is my own." He thought out part and filled in the rest by force of habit, association, or rash inference. And the like may be affirmed of every case of error. A man has worked out a long mathematical problem: he assents to the conclusion, but not from clear insight of what is involved in it; his assent is given in trust that his working out of a long process was right at each step. But some step or steps there must have been which he never represented in thought, and so "the error was not really thought."

Somewhat in the spirit of these last explanations, it has been said, that if the old astronomers had only stated the limits under which they were speaking, their statements would have been correct. They assumed that there was an absolute upside, opposed to an absolute downside: they assumed that men could not stand on the earth if it were placed upside down: from these premisses their inference was valid, that the earth could not be revolving. From the hypothesis of a stationary earth, they rightly inferred the motion of the sun. Thus they never fully thought out the real problem, but an ideal problem which was consistent with itself. Not thought, but something else, carried them over some parts of their argument when they applied it to the actual system: but if they had put in their limits, then their view would have been hypothetical and right. Instead of taking the absolute form, "The earth is fixed, the sun revolves round it," their astronomy would have taken a hypothetical shape, "If certain suppositions are true, then the earth is fixed and the sun revolves round it."

To put the whole of this part of our doctrine summarily: the error assented to is either a contradiction in terms, and then it is clear that it has never been strictly an object of thought, or it is an error in a contingent matter, and then the final result may in some sense be said to be an object of thought, but at least its actuality has never properly been thought out to the full. We may really think that X was intoxicated when he was not; but we have never followed out in thought all the evidences for the fact. At some point, not thought, but another power, has effected a part of the process.

In this way Hamilton's saying, which is in conformity with the scholastic theory of error, if not made to mean more than it necessarily implies, expresses a useful doctrine. It corresponds to that which Descartes probably meant when he said that, if he was only careful always to follow clear ideas, and nothing else, he could never go wrong. Unfortunately he did not describe properly the criterion of clear ideas; but we may add the explanation, that clear ideas must mean insight into objective truth. Insisting on this insight, we necessarily assign a very different account of the genesis of error from that which is assigned by those who treat only of the mechanism or chemistry of ideas; of associations and dissociations, of affinities and repulsions between mental atoms. Once more it is seen how a philosophical explanation is dependent on the radical nature of a system; and how the followers of Hume are in their whole point of view at variance with truth. A theory so erroneous as Hume's can never render the right account of error, though it may serve as an illustration of it to an expounder who goes on true principles. On these true principles we have laid down our theory, that ignorance is a condition, but is never by itself alone the efficient cause of error, and never identical with error: that the ignorant mind is necessarily fallible, but not with the same necessity actually false: that the man who labours under incomplete and obscure ideas is essentially exposed to the danger of judging wrong, but does not so essentially judge wrong in fact; that habits and associations incline us to assert more than is in the evidence before us; and finally that the will exerts its power to urge on acts of assent or dissent, which the mere intellect of itself would not have made, because these being untrue, are not fit objects to decide an intellectual movement. The grossest mistake must have some element of truth in it; and "falsehood is dangerous only from its possessing a certain portion of mutilated truth." Thus evidence itself helps to elicit the erroneous judgment; but it is precisely because, besides evidence, there are other forces at work, that the total result is a failure.


(1) In saying that our ignorance is infinite compared with our knowledge, we must be taken as referring, to the details which in any concrete enunciation are left to be filled in: for, of course, under the generalized terms Being, Substance and Accidents, God and Nature, we include all things in our knowledge.

(2) When distinguishing will from intellect, we require no more than such a distinction as all admit who allow that to know a thing is not the same as to wish it. This leaves quite intact the question whether the several faculties of the soul have a real distinction inter se, and from the soul to which they belong. Some of our modern English writers assert that every mental act contains an element of thought, feeling, and volition, the three constituents of mental life. It may be true that the intellect never embraces truth, which the will does not somehow, at the same time, embrace, at least for its truth's sake, though under other respects the will dislikes the object intensely. Yet, on no account could we admit the Malebranchian theory, that the assent in a judgment is the act, not of the intellect, but of the will.

(3) A further question is whether the action of the will in error is always free. Suarez{a} speaks as though it were; but allows such a minimum of freedom sometimes as would save from moral guilt. In accordance with his teaching, we hold the existence of countless limitations upon that freedom, especially in what are called "first motions of the will," the motus primo primi of theologians. Very often, at any rate, our errors are proximately or remotely due to an abuse of freedom: but we may refrain from saying, that they are so always.

(4) The importance of the power of will in determining judgment has, besides a high speculative, an equally high moral importance. It is an undoubted fact, that the erroneous judgments of many persons are most culpable. We have only to note what an abatement of assertions there is, as soon as an ordinary talker is brought to book, and as it were put on his oath, to infer how very rash are a great mass of human assents. It is said that many would sooner have their good will than their sound judgment called in question: they prefer to confess a culpable negligence rather than an inculpable mistake. But the two departments are connected; so that a man cannot constantly be guilty of great wilfulness in his judgments, without intrinsically damaging his very power to know the truth. In the interest of his intellectual faculty itself he must exercise a most vigilant use of his will, as a determinant of his assent.

{1} There is a certain semblance of truth in the caution given by Rousseau: "Remember, always remember, that ignorance has never done any harm, and that only error is mischievous; that a man is riot led astray by what he does not know, but by what he wrongly fancies that he knows." (Emile, Lib. III. in initio.) In a later passage towards the end of the same Book III., he returns to the subject: he says that all our errors come from judging; if only we had no need to judge, we should avoid error, and should be happier in our ignorance than our knowledge can make us. He thinks that learned men have less of truth than the unlearned, because each truth that they take up is accompanied with a hundred false judgments; so that the most famous of our learned societies is only a school of falsehood, and there are more mistakes in the Academy of Sciences than among a body of Hurons. "Since then the more men know the more they fall into mistakes, the only way to escape error is ignorance. Never judge, and you will never deceive yourself. This is the lesson of Nature as well as of reason." He adds, however, that as circumstances force us to form judgments, we had better study how to form them rightly.

{2} See Bk. I. c. iv. p. 52.

{3} "Quod in errores incidimus defectus quidem est in nostra actione, sive in usu libertatis, sed non in nostra natura. . . . Jam vero cum sciamus errores omnes nostros a voluntate pendere, mirum videri potest, quod unquam fallimur, quia nemo est qui velit falli." (Principia, Part I. nn. 37, 39.)

{4} "Sed longe aliud est velle falli, quam velle assentiri iis in quibus content errorem reperiri. Et quamvis revera nullus sit qui expresse velit falli, vix tamen ullus est qui non saepe velit iis assentiri in quibus error, ipso inscio, continetur." (1.c.)

{5} See his twenty-fourth lecture on the History of Philosophy, where he treats Locke's theory of error: "La pure erreur serait impossible, et elle serait inintelligible: comme l'erreur ne pénètre dans l'esprit d'un homme que par le côté de vérité qui est en elle."

{6} Logic, Vol. II. Lectures xxix., xxx.

{7} Prolegomena Logica, p. 250. See Hobbes on Error, Leviathan, Part I. c. v.; and Hume, Treatise, Bk. I. Part IV. § 1.

{8} Intuitions of the Mind, Bk. II. c. ii. § 2; Bk. IV. c. ii. § 2.

{9} De L'Intelligence, Part II. Liv. I. c. i. pp. 411, seq.

{10} On Illusions (International Series), pp. 60, seq. pp. 111, seq.

{11} The subject has been already discussed in c. vii.

{12} The Hamiltonian school adhere for the most part to this doctrine. Thus, besides Mansel, we find Professor Veitch saying: "There is only one way of thinking by the understanding, that is, the legitimate way. Any other is mere illusion, not a reality of thought at all." (Institutes of Logic, p. 7.)

{a} Metaphysics, disp. ix. § 2.

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