I.

DAVID HUME REDIVIVUS.

Mr. Charles S. Peirce’s article entitled “The Doctrine of Necessity Examined,” which appeared in the last number of _The Monist_, must have been a surprise to many thinking readers. It must have affected them in a somewhat similar manner as Hume’s “Treatise of Human Nature” affected Kant. It roused him from his dogmatic slumber: He abandoned dogmatism but nevertheless did not accept Hume’s skepticism; he remained positive; yet he propounded a better positive view than was the old dogmatism; he established in philosophy the method of critique.

The parallelism between David Hume, who doubted the validity of our conception of causation, and Mr. Charles S. Peirce who denies the universality of the doctrine of necessity, is very marked in more than one respect. It is, in spite of many differences, a case of close analogy, and the answer which we shall have to give to either, will in many respects be suited to both. Both shake the ultimate ground of scientific research at its very root. Both call in question the most fundamental concept upon which all our methods of investigation and philosophy rest. Both challenge the reliability of an idea of which few would hesitate to say that it is all but universally accepted. In fact the ideas “causation” and “necessity” are more than kin. If analysed, many of their elements will be found to be actually identical. Thus the one cannot be either established or doubted without establishing or doubting the other. Accordingly Mr. Peirce, in some respect, repeats David Hume’s onslaught upon the current conception of the basis of human knowledge with the more formidable weapons which a century of close thought and scientific investigation have furnished him.

If Kant’s answer to Hume had been satisfactory, Mr. Peirce probably would not have renewed the attack or he would have had to modify it considerably. Kant, however, whom we both, Mr. Peirce as much as I myself, admire as a master of philosophic thought, did not solve the question satisfactorily. Yet Kant pointed out the way of solving it, which was the middle way between dogmatism and scepticism, called by him and his followers “Criticism,” and it is this way on which we trust is safest travelling.

Mr. Peirce is right that the doctrine of necessity cannot be “postulated,” for “to postulate a proposition is no more than to hope it will be true.” The doctrine of necessity is, indeed, usually treated as a postulate, and Mr. Peirce’s attack appears formidable because he shows the weakness of the arguments which are commonly brought forward in its favor and which we grant to be insufficient.

Mr. Peirce says (_The Monist_, II, 3, p. 330):

“In view of all these considerations, I do not believe that anybody, not in a state of case-hardened ignorance respecting the logic of science, can maintain that the precise and universal conformity of facts to law is clearly proved, or even rendered particularly probable, by any observations hitherto made. In this way, the determined advocate of exact regularity will soon find himself driven to _a priori_ reasons to support his thesis. These received such a sockdologer from Stuart Mill in his Examination of Hamilton, that holding to them now seems to me to denote a high degree of imperviousness to reason; so that I shall pass them by with little notice.”

Mr. Peirce is right when saying that necessitarianism must be founded on something other than observation. Observation is _a posteriori_; it has reference only to single facts, to particulars; yet the doctrine of necessity, if there is anything in it at all, is of universal application. The doctrine of necessity, let us not be afraid to pronounce it clearly, is of an _a priori_ nature. The scientist assumes _a priori_, i. e. even before he makes his observations or experiments, as a general law applicable to every process which takes place, that, whatever happens, happens of necessity in consequence of a cause and in conformity to law, so that the same cause under the same circumstances will produce the same effects. If all the _a priori_ reasons, as Mr. Peirce maintains, received a sockdologer from Stuart Mill, then indeed we shall have to abandon the idea of necessity as the superstition of a past and erroneous philosophy and we shall have to start the world of science over again.

Mr. Peirce denies the strict regularity of natural law and introduces an element of chance. He says (ibid. p. 336):

“To undertake to account for anything by saying boldly that it is due to chance would, indeed, be futile. But this I do not do. _I make use of chance chiefly to make room for a principle of generalization, or tendency to form habits, which I hold has produced all regularities._[73] The mechanical philosopher leaves the whole specification of the world utterly unaccounted for, which is pretty nearly as bad as to boldly attribute it to chance. I attribute it altogether to chance, it is true, but to chance in the form of a spontaneity which is to some degree regular.”

Mr. Peirce is the pathfinder of a new and as yet untried road. He strikes out boldly into the tumultuous ocean of chance, hoping to find in his journey the connection between the East and the West, between contrasts that seem to him otherwise unconnectible. The confidence of the bold discoverer is set forth in the warnings he gives to all seafaring people. He attempts to frighten the ill-informed minds who might innocently venture out in other directions; and he will thus naturally prevent many from falling either into the Charybdis of doubting the propriety of applying the logic of probabilities to the problem of necessity and causation in general, or, worse still, into the Scylla of the _a priori_. The former, he tells us denotes “a state of case-hardened ignorance respecting the logic of science,” the latter “a high degree of imperviousness to reason.”

Mr. Peirce is well known as one of the keenest logicians now living. Considering this fact I am slow to take up arms against him in defending a case which he so strongly brands beforehand. I must from the beginning plead guilty to a belief in necessity, and having critically revised my view once more I cannot help upholding it. I am fully conscious of the fact that hundreds, thousands, and millions of single experiences (which in Kantian terminology are called _a posteriori_ arguments) cannot establish a solid belief in necessity, nor can any imaginable number of sequences prove the rigidity of causation, and I confess freely that I support my thesis with _a priori_ reasons. Yet at the same time attention must be called to the fact that neither Mr. Hamilton nor Mr. Mill had any adequate conception of the _a priori_, and Mr. Mill’s sockdologer does not disturb in the least the assurance of my view; for the _a priori_ can, in my opinion, be based upon the firm ground of experience.

All the many sense-experiences at our command, if considered singly, cannot constitute knowledge. In order to weave the woof of the _a posteriori_ into coherent cloth we want the warp of the _a priori_, and I do not see how we can do without it. But the _a priori_ is not that mystical hocus-pocus of absolute truth with its impertinent assumptions such as it is presented by pseudo-Kantians and justly denounced by Mill; it is not as Mr. Peirce brands it an “I cannot help believing,” it is not a “natural belief,” nor is it as others conceive it an innate idea. It is, briefly described, simply and solely formal knowledge, such as 2 × 2 = 4, to which we attribute universality and necessity and with the assistance of which we are enabled to predict and predetermine certain results beforehand (i. e. _a priori_). We might invent a new name for the _a priori_, the latter having become odious through the denunciations of its enemies and worse still, having been distorted beyond recognition through the misuse to which it was put by its defenders and suppositional friends. Yet that would be another question, and the idea of the _a priori_, i. e. of formal knowledge involving universality and necessity would remain the same.

The universality and necessity of formal knowledge are as a rule taken for granted by scientists. But philosophy can take nothing for granted, and the problem rises: How is the belief in the universality and necessity of formal knowledge to be justified? Mr. Peirce’s onslaught on the doctrine of necessity is a challenge to answer this question.