Charles S. Peirce
Logic, Truth, and the Settlement of Opinion
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MS 179 (Robin 364, 721): Writings 3, 14-16
Winter-Spring 1872

[Editorial Note (Ransdell): As presented here the document is modified by editorial paragraphing intended to make the implicit logical structure as clear as possible, with some minor modifications of punctuation to enhance perspicuity. Anything appearing within brackets is editorial in origin. Peirce's emphasis is shown by combining underlining and italics in order to compensate for the tendency of HTML fonts to be too feeble in showing the kind of contrast on-screen that is wanted when emphasis is intended.
        Although these modifications are relatively trivial in the case of this particular document, even minor editorial changes can introduce biased interpretation. Hence the version of it exactly as presented by the editors of volume 3 of The Writings of Charles S. Peirce is also being made available here, for purposes of scholarly comparison, in the text box below.]

        Logic is the doctrine of truth, its nature and the manner in which it is to be discovered.

        The first condition of learning is to know that we are ignorant. A man begins to inquire and to reason with himself as soon as he really questions anything and when he is convinced he reasons no more. Elementary geometry produces formal proofs of propositions which nobody doubts; but that cannot properly be called reasoning which does not carry us from the known to the unknown, and the only value in the first demonstrations of geometry is that they exhibit the dependence of certain theorems on certain axioms—a thing which is not clear without the demonstrations. When two men discuss a question, each first endeavors to raise a doubt in the mind of the other, and that is often half the battle. When the doubt ceases there is no use in further discussion. Thus real inquiry begins when genuine doubt begins and ends when this doubt ends. And the premises of the reasoning are facts not doubted. It is therefore idle to tell a man to begin by doubting familiar beliefs unless you say something which shall cause him really to doubt them. Again, it is false to say that reasoning must rest either on first principles or on ultimate facts. For we cannot go behind what we are unable to doubt; but it would be unphilosophical to suppose that any particular fact will never be brought into doubt.

        It is easy to see what truth would be for a mind which could not doubt. That mind could not regard anything as possible except what it believed in. By all existing things it would mean only what it thought existed, and everything else would be what it would mean by non-existent. It would, therefore, be omniscient in its universe. To say that an omniscient being is necessarily destitute of the faculty of reason sounds paradoxical; yet if the act of reasoning must be directed to an end, when that end is attained the act naturally becomes impossible.

        The only justification for reasoning is that it settles doubts, and when doubt finally ceases, no matter how, the end of reasoning is attained. Let a man resolve never to change his existing opinions, let him obstinately shut his eyes to all evidence against them, and if his will is strong enough so that he actually does not waver in his faith, he has no motive for reasoning at all, and it would be absurd for him to do it. That is method number one for attaining the end of reasoning, and it is a method which has been much practised and highly approved, especially by people whose experience has been that reasoning only leads from doubt to doubt. There is no valid objection to this procedure if it only succeeds. It is true it is utterly irrational; that is to say, it is foolish from the point of view of those who do reason. But to assume that point of view is to beg the question. In fact, however, it does not succeed; and the first cause of failure is that different people have different opinions and the man who sees this begins to feel uncertain.

        It is therefore desirable to produce unanimity of opinion and this gives rise to method number two, which is to force people by fire and sword to adopt one belief, to massacre all who dissent from it and burn their books. This way of bringing about a catholic consent has proved highly successful for centuries in some cases, but it is not practicable in our days.

        A modification of this is method number three, to cultivate a public opinion by oratory and preaching and by fostering certain sentiments and passions in the minds of the young. This method is the most generally successful in our day.

        The fourth and last method is that of reasoning. It will never be adopted when any of the others will succeed and it has itself been successful only in certain spheres of thought. Nevertheless those who reason think that it must be successful in the end, and so it would if all men could reason. There is this to be said in favor of it. He who reasons will regard the opinions of the majority of mankind with contemptuous indifference; they will not in the least disturb his opinions. He will also neglect the beliefs of those who are not informed, and among the small residue he may fairly expect some unanimity on many questions.

        I hope it will now be plain to the reader, that the only rational ground for preferring the method of reasoning to the other methods is that it fixes belief more surely. A man who proposes to adopt the first method may consistently do so simply because he chooses to do so. But if we are to decide in favor of reasoning, we ought to do so on rational grounds. Now if belief is fixed, no matter how, doubt has as a matter of fact ceased, and there is no motive, rational or other, for reasoning any more. Any settlement of opinion, therefore, if it is full and perfect, is entirely satisfactory and nothing could be better. It is the peculiarity of the method of reasoning, that if a man thinks that it will not burn him to put his hand in the fire, reasoning will not confirm that belief but will change it. This is a vast advantage to the mind of a rationalist.

        But the advocate of any one of the first three methods will be able to say (if either of those methods will yield a fixed belief) either that he knows by his method that fire will burn, so that reasoning is inferior to his method in that it may permit a man for a moment to doubt this, or else that he knows that fire will not burn, so that reasoning leads all astray. In either case therefore he will conceive that that which to the rationalist seems the great advantage of reasoning to be a great fault. Thus the only ground of a fair decision between the methods must be that one actually succeeds while the others break up and dissolve. Bryant expresses the philosophy of the matter perfectly

                        Truth struck to earth shall rise again
                        The eternal years of God are hers
                        While error . . . writhes in pain
                        And dies amidst her worshippers.

Document as presented in Writings of Charles S. Peirce, vol. 3, 14-16

Logic is the doctrine of truth, its nature and the manner in which it is to be discovered.         The first condition of learning is to know that we are ignorant. A man begins to inquire and to reason with himself as soon as he really questions anything and when he is convinced he reasons no more. Elementary geometry produces formal proofs of propositions which nobody doubts, but that cannot properly be called reasoning which does not carry us from the known to the unknown, and the only value in the first demonstrations of geometry is that they exhibit the dependence of certain theorems on certain axioms, a thing which is not clear without the demonstrations. When two men discuss a question, each first endeavors to raise a doubt in the mind of the other, and that is often half the battle. When the doubt ceases there is no use in further discussion. Thus real inquiry begins when genuine doubt begins and ends when this doubt ends. And the premises of the reasoning are facts not doubted. It is therefore idle to tell a man to begin by doubting familiar beliefs, unless you say something which shall cause him really to doubt them. Again, it is false to say that reasoning must rest either on first principles or on ultimate facts. For we cannot go behind what we are unable to doubt, but it would be unphilosophical to suppose that any particular fact will never be brought into doubt.         It is easy to see what truth would be for a mind which could not doubt. That mind could not regard anything as possible except what it believed in. By all existing things it would mean only what it thought existed, and everything else would be what it would mean by non-existent. It would, therefore, be omniscient in its universe. To say that an omniscient being is necessarily destitute of the faculty of reason, sounds paradoxical; yet if the act of reasoning must be directed to an end, when that end is attained the act naturally becomes impossible.         The only justification for reasoning is that it settles doubts, and when doubt finally ceases, no matter how, the end of reasoning is attained. Let a man resolve never to change his existing opinions, let him obstinately shut his eyes to all evidence against them, and if his will is strong enough so that he actually does not waver in his faith, he has no motive for reasoning at all, and it would be absurd for him to do it. That is method number one for attaining the end of reasoning, and it is a method which has been much practised and highly approved, especially by people whose experience has been that reasoning only leads from doubt to doubt. There is no valid objection to this procedure if it only succeeds. It is true it is utterly irrational; that is to say it is foolish from the point of view of those who do reason. But to assume that point of view is to beg the question. In fact, however, it does not succeed; and the first cause of failure is that different people have different opinions and the man who sees this begins to feel uncertain. It is therefore desirable to produce unanimity of opinion and this gives rise to method number two, which is to force people by fire and sword to adopt one belief, to massacre all who dissent from it and burn their books. This way of bringing about a catholic consent has proved highly successful for centuries in some cases, but it is not practicable in our days. A modification of this is method number three, to cultivate a public opinion by oratory and preaching and by fostering certain sentiments and passions in the minds of the young. This method is the most generally successful in our day. The fourth and last method is that of reasoning. It will never be adopted when any of the others will succeed and it has itself been successful only in certain spheres of thought. Nevertheless those who reason think that it must be successful in the end, & so it would if all men could reason. There is this to be said in favor of it. He who reasons will regard the opinions of the majority of mankind with contemptuous indifference; they will not in the least disturb his opinions. He will also neglect the beliefs of those who are not informed, and among the small residue he may fairly expect some unanimity on many questions.         I hope it will now be plain to the reader, that the only rational ground for preferring the method of reasoning to the other methods is that it fixes belief more surely. A man who proposes to adopt the first method may consistently do so simply because he chooses to do so. But if we are to decide in favor of reasoning, we ought to do so on rational grounds. Now if belief is fixed, no matter how, doubt has as a matter of fact ceased, & there is no motive, rational or other, for reasoning any more. Any settlement of opinion, therefore, if it is full and perfect, is entirely satisfactory and nothing could be better. It is the peculiarity of the method of reasoning, that if a man thinks that it will not burn him to put his hand in the fire, reasoning will not confirm that belief but will change it. This is a vast advantage to the mind of a rationalist. But the advocate of any one of the first three methods, will be able to say (if either of those methods will yield a fixed belief) either that he knows by his method that fire will burn, so that reasoning is inferior to his method in that it may permit a man for a moment to doubt this, or else that he knows that fire will not burn, so that reasoning leads all astray. In either case therefore he will conceive that that which to the rationalist seems the great advantage of reasoning, to be a great fault. Thus the only ground of a fair decision between the methods must be that one actually succeeds while the others break up and dissolve. Bryant expresses the philosophy of the matter perfectly                         Truth struck to earth shall rise again                         The eternal years of God are hers                         While error . . . writhes in pain                         And dies amidst her worshippers.