1. You ask “my idea on the impossibility of proving the truth of First Principles?”

By “truth” you mean the ascertained existence of any idea or thing, and the ascertained consistency of any statement with some such idea or thing.

By “principles” you mean not simply cardinal propositions, but cardinal propositions that we have ascertained to be true.

By “first principles” you mean the indubitably true but unprovable elementary principles of all our knowledge. You mean that these principles are the ground whereon we build in our reasonings; all that we build upon them must, in consequence of being so built, admit of being “proved” whether we have built rightly—that is, admit of being subjected to the test whether the reasoning is correct; but these “first principles” are confessedly exempted from this test, and yet are received as true, no less than the others that have sustained this ordeal. You ask the meaning of this privilege, whether it is right; and, if so, to what propriety or necessity of the case it is due?

2. You ask, “How is truth ascertained to be truth?” or, in other words, “What is the criterion of truth?”

With respect to the first query—In accordance with the definition I have above given of truth, it would seem that it must have two sources, experience and reason, experience who notifies the existence of certain ideas or things, and reason, who forms propositions suggested by them. Experience, therefore, acts the simple part of supplying all the materials of truth; while reason, besides his acknowledged office of judge of all truth, exercises the quite different function of being himself the purveyor of a portion of it.

So indubitable is it that truth can have these two sources only, that even fanaticism would be found confessing the principle; while it appeals to the experience of those who agree with it, as well as professes to be reasonable.

First principles must, accordingly, be of two kinds. Of those that are based upon experience, I will give the following instances:—I hear the chirping of a bird, and I see an inkstand before me. That I have the sensation of hearing and seeing in these two cases, are facts of which it is impossible I can doubt. Reason perceives that these are primary facts or first principles, neither admitting nor requiring any proof, testified by consciousness, and self-evidently verified on that testimony.

By reason, of course is meant the reason of all mankind—that is, of all who are presumably competent to judge on the subject. So that any just or reasonable confidence in the verdict of my own reason—in this or in any other matter, presupposes a due comparison of my own reason with that of others, nay, in some cases, a consideration of the supposably more enlightened reason of future times.

I discriminate first principles from derived ones thus:—“I see the sun,” is a first principle to me; “you see it,” is a first principle to you; by comparing these two ideas, each attains the derived principle that the other sees what he does, and the further derived principle that the sun is an existence independent of both. His own existence is, indeed, to every one the first principle, by means of which he infers the existence of other things and beings.

In coming now to the other kind of first principles, consisting of propositions formed by reason, we perceive that these show symptoms of still further difference from the above, than that which results from the difference of their source, of difference that affects their philosophical character, and their technical right to the name under which they present themselves to us. In short, the primary philosophy has not yet settled their title.

They are perceived by us to be true by an act of reason called intuition. Not similarly, however, does our reason inform us that they really are first principles, and our science is hitherto unequal to this inquiry.

Take, for instance, the following celebrated thesis, so often cited as the most fundamental of all the propositions of reason, insomuch as to be tacitly implied in all our reasonings; which yet we are not sure is a first principle, all that can be said in favor of its pretensions being that we can find no one who is able to reduce it to more primary elements:—

It is impossible for a thing at the same time to be and not to be.

Any one agreeing, as every one must, that this is true, might still justly put the query, Why is it impossible? thereby calling its assertion in question, demanding its credentials of proof, seeking some ground for its truth other than its own testimony, and hypothesising some other proposition more fundamental than it of which it would be a derivative, and by all and each of these proceedings, rejecting its claim to be a first principle.

Its resisting our analysis is a good subjective ground for our ranking this and other similar propositions among our first principles. But they could only have the true claim by its being made clear that the inability results from the nature of the case, and not from our own incompetency.

This test is borne by the former description of first principles; we are able to see that the instances I adduced, such as the statements, “I see the sun,” “I see an inkstand,” “I hear a bird,” “I am conscious that I exist,” evade our power of ordinary proving, because they do not admit of such proof.

When we perceive that no one can answer this query, we are prompted to another. Why cannot we answer it? whence our inability? what prevents us? But here also we find ourselves completely in the dark, which is somewhat strange, considering that in every human pursuit, whether of science or any other, when we wish to do a thing and cannot do it, we are generally able to specify some particular, either of self-defect or outward impediment that is supposed to be in fault. But I imagine, if the reader were to experiment on the specimen I have given, he would not only find himself to fail in solving the problem, Why is it that a thing cannot at once be and not be? but would not have a word to advance in the way of accounting for his failure.

These remarks apply to all other propositions of the sort. Euclid’s axioms, which undoubtedly aim to be as elementary as possible, and therefore may be said to aim to be first principles, are confessedly, under this aspect, unsatisfactory to the learned. “Things that are equal to the same are equal to each other.” Every one is inclined to ask, Why? “A straight line is the shortest distance between two points.” Again, Why?

The sum of the above strictures on this kind of so-called first principles, is—1. That they have not made good their title, and therefore are not to be accredited with it. 2. That there is a decided presumption against that title from the doubt and dissatisfaction with which it is met, where want of candor and intelligence cannot be imputed, especially when it is considered that the other, the sensuous experimental kind of first principles, have so frank an acceptance. 3. It seems to be absolutely provable, and I suppose I have above incidentally proved it, that they are not first principles. 4. The task is set to metaphysics of supplying the most satisfactory proof of all by bringing to light such propositions as would be perceived to underlie these so-called first principles, and to be the real first principles to which the others would give precedence.

As regards their name, it being so much in point, excuses the old remark that the elements of our knowledge stand in a reversed order in respect to this knowledge to what they assume in our process of acquiring it. A first principle, therefore, means also a last one; it is the last in whatsoever endeavors to descend to the bottom or to penetrate to the source of our knowledge, but it becomes the first when we trace it from this source through its derivative ideas.

The investigating act should not be confounded with the prospecting one. The sensible horizon of subjective vision can, by no mediation, be exalted into the real horizon of truth, wherein the genuine first principles that bound human capability are exclusively to be found.

It may be asked, apart from the inquiry what first principles there are, Is there a necessity that some first principles should be? So it seems from the data of the case. It is patent to common observation that the mind of man is recipient of ideas from the things that surround it. The contact of its apprehending faculty with the things it apprehends, must, it would seem, constitute first principles. After it has got them it might conceivably elicit from them derived principles, but the original ones cannot be thus derived, since there are none earlier from which to derive them.

Again, it is to be inquired, Does the mind, in receiving its ideas, possess and exercise in reference to the things on which it operates, a copying faculty or a transforming faculty? Does it import them simply in their native character, in the way a mirror does the object it reflects, or does it manufacture, cook, and assimilate them, so as to change them into something partaking of its own?

And, if it changes them, what is the extent of the change? Does it go so far only as the semi-idealism of Locke, or extend into the absolute idealism of the German school?

Because these questions have been wont to puzzle either the learned, or the public, or both, it does not follow that they are difficult. I suppose them to admit of decided answers before a supposed competent audience.

As I am unprovided with proof, although I suppose it is to be provable, that first principles of reason must needs be, I must speculate for a moment on the possibility of a proposition of the form of “two and two make four,” being derived from one of the form of “I scent the rose,” for this seems to be the alternative of there being no first principles of reason. Evidently I must confess to having no grounds for pronouncing such a derivation impossible, though I must grant it to be paradoxical. Our mal-cultivation of non-material science, and the imperfection of our metaphysics, is probably the only cause of the strange predicament.

No doubt M. Cousin, and several other eminent teachers of youth, to whose office it belongs to expound received metaphysics, have comprised First Principles in their course of philosophy; but as I have barely met with any of their writings, I must confess such an ignorance of them, as not even to know how far I am either adopting, or evading their phraseology, in discussing the same subjects. Mine, however, cannot be wrong, since the term “first principles,” that I have chosen, is one of familiar popular use; so that were this mode of speech, as indeed it is, peculiarly liable to ambiguity, it would, for that very reason, be preferable to any other, till such time as that ambiguity should have been explained, and the wrong thinking, of which it might have been the source, exposed and obviated. Not till this had been done would it be time to inquire whether the current metaphysics had invented any intrinsically better ways of speaking on these topics, for though the veriest tyro in such investigations would be justified in objecting to some of its technicalities, such as the invention of the word free-will, for instance, for the same reason that a beginner in zoology might object, were such an attempt ever made, to the introduction of the word sphynx or griffin into that branch of inquiry, there can be no doubt that other of its speculations are more happily conceived. Hence I suppose it would be a decided mistake to imagine, for example, that no trouve whatever is to be elicited from the obscurities of Kant, but on the other hand, one must as much take care to entertain sober conjectures of the possible value of such unsunned treasures, as to keep in mind that quackery may be not unqualified with some merit, and I might surmise that it was perhaps in virtue of his fabulous expectations in this direction, that Coleridge could not execute his long-meditated plan of elucidating that writer; or rather, perhaps—to speak more curtly—a spirit more differing from that which compounded the amalgam, was necessary to resolve and detect it.

According to this estimate of the value of our achieved studies, it would be expectable, in regard to my present topic, that almost all the materials for right conclusions on it must be extant somewhere or other in our books, no great amount of ability being required to turn them to proper account: an easily suppliable desideratum being thus left unsupplied, the public indifference manifested thereby would seem to bear the ascription of our unsatisfactory metaphysics to the fault, however apportioned between the many and the few, not of the intellect, but of the reason.

Indeed, it is held as a pretty general rule, that where there is want of reform, there is want of reason; and Bacon, by implication, thought the rule here applicable, when, in defending his “new philosophy” from the charge of arrogance, he apologised by saying that a “cripple in the right road would make better progress than a racehorse in the wrong.” That is, he claimed for himself, as he was bound logically to do, the plain good sense of directing his supposably humble faculties with an obvious regard to the end he proposed and professed, and he was ready to concede to his competitors all kinds of superiority but this.

The same simplicity characterises the reforming animus of the other great patriarch of “the new philosophy,” in its sister branch. The still debated point between the school of Locke and the old philosophy was, and is, of such a form as may be figured by the following hypothetical, and it may be, well-founded statement. Locke seems to have battled mainly for the principle that ideas that every one allows to be inferences, should be acknowledged by philosophy to be such, while the adherents of the old ideas maintained, in opposition to him, that ideas that every one allows to be inferences, should not be acknowledged by philosophy to be such. Or, in other words, Locke aimed to realise a certain first principle of reason, which I shall have hereafter to consider, which stands thus:—“That which it is,” while his opponents withstood this innovating pretension, finding it fatal to their doctrine. If the reader is somewhat startled at the statement I have just made, I will remind him that it amounts to nothing more than saying that in the contest between the new and the old philosophy, reason is entirely and absolutely on the side of the former, an assertion which, of course, I must both think admits of being substantiated, and must take myself, in some degree, to be able to aid in its being so.

The existing quarrel between the two philosophies might, perhaps, be personified through the medium of a principal champion on each side. For the new ideas I could only choose Locke, since he is admitted to have had no equally eminent successor; for the old I would choose M. Cousin, both on account of his superior merit and popularity, and also of his having made Locke the subject of some elaborate strictures that I happen to have read. On these, when they come again to hand, I should perhaps have something to remark; meanwhile I must content myself with addressing myself to one of them in the following manner:—

In antiquity and the middle ages, the schoolmaster and the philosopher were one and the same individual. The new philosophy was the first to separate these two departments; perceiving that the communication of truth is a distinct office from its investigation, and that that difference of office in each case necessitates a corresponding difference in the public, that is the proper object of its exercise. Since, moreover, society may be discriminated into two sorts of mind, admitting of being pictured as the childish and the adults, it is evident that the instructor must find his audience more especially in the former, while the investigator of truth must appeal exclusively to the latter. This he must needs do, to whichever of the sciences he ministers; and not only so, but he must more particularly address himself to a small and select portion of this itself selecter class, constitute them the witnesses and judges of his proceedings, and perceive that both his success in philosophy and the acknowledgment of it can only be founded first and foremost on their approbation. As even in jockeyism and prize-fighting, there are “the knowing ones,” similar referees are, by the nature of things, required for the flourishing estate of any science; and evidently in proportion as they might be incompetent to such an office, false or imperfect science must be the result.

Locke, acting on this instinctive view, communicated to the public certain observations he had made in mental philosophy, and entitled his work, An Essay on the Human Understanding. He properly called it an essay, because a person who simply aims to investigate truth, undertakes to do his best in the way of trial, endeavor, and experiment, in such sort as to make the word essay appropriate to what he does. The word moreover implies that the thing done, though it is the writer’s best, is liable to be incomplete, comparatively imperfect, and, indeed, in the more difficult questions of philosophy, as well as in the less advanced stages of philosophising, is sure to be so. Locke accordingly, having had his attention struck with certain phenomena of the human mind, told the public just what he had observed, and nothing else. Among the observations that he thus imparted, was the process through which the mind seems to go in arriving at the sum of its ideas, and especially the points from which it seems to start in this process.

M. Cousin, having apparently no conception of a way of acting so proper to legitimate inquiry, and having himself written a Course of Philosophy, evidently thinks Locke ought to have done the same; for he says that Locke is erroneous in the method of his philosophy, that he begins at the wrong end, that instead of having told us as he has how the ideas arise in the mind, he ought to have told us what the ideas are, instead of describing their origin to have described their actuality, to have given a list of the faculties of the mind, and so on. Which is just the same thing as saying that a traveller who publishes his explorations in America, ought instead to have gone to China.

I shall have to make some objections to Locke, but they will be of a nature exactly contrary to those of which he is usually made the subject. Instead of accusing his principles I shall have to impute to him the not sufficiently carrying them out; a fault due to his position as an early reformer, and perfectly consistent with his high character as such.

I have the more reason to note this distinction between M. Cousin’s department and the function exercised by Locke, because I am forced myself to take the benefit of it. Want of erudition would form very vulnerable points, were I to be judged by the former standard. In the little I have yet put forth on the subject of First Principles, I already find two or three errors of that sort, which a greater amount of reading would no doubt have enabled me to escape. My present letter may close with some correction of one of these.

Preliminary, I will venture to call “That which is is,” a first principle of reason, and “Two and two make four,” one of its derivatives, leaving this topic for future explanation, and then proceed thus:—When in my last letter I represented first principles as bounding the horizon of human knowledge, I left it to be inferred that both the kinds of “first principles” I had mentioned were thus describable in common. I find, however, that this metaphysical character belongs exclusively to first principles of sensuous experience, and no more belongs to first principles of reason than to first principles of grammar, or to first principles of rhetoric. That is, first principles of reason are merely the result of one of those analytical inquiries in which we arrive at something absolutely simple, and must there stop, just as in the science of numbers we may thus arrive at unity.

Having long ago defined First Principles of sensuous experience, I find there is a difficulty attached to the other kind of first principles derived from the various use of the word reason—which I will say betrayed me into a wrong inference in the concluding paragraph of my last letter.

Locke, in the 17th chapter of his fourth book, confesses that this word, in the proper use of the English language, is liable to bear several senses. Due discrimination in such a case, and a cautious avoidance of the dangers to which philosophy is exposed, and has so amply incurred, from this kind of source might, above all, have been, expected from Locke, since he was the first who inculcated it, and is generally remarkable for the observance of his own precepts in this matter. Hence the charge I have now got to bring against him is a little surprising.

Indeed, it might be asserted that his position and circumstances do not seem very readily to bear the entire responsibility of some of his proceedings. Perhaps he might be characterised as a writer of somewhat humorous idiosyncracy in respect to tendency to fixed ideas. His lapses, indeed, are not many, but they are highly significant, as I shall have occasion in more than one instance to show, and among these must evidently be reckoned that I am now going to notice, since it imports the wrong definition of a word of such cardinal meaning.

In defining the word reason, in its proper and specific sense wherein it is used to denote a certain well-known quality of the human mind—that is, as approvedly ascertained and appreciated under this name, as are certain weights and measures under those of pound, gallon, or mile, he assigns a meaning to it that comes short of the proportions thus justly prefigured as belonging to it. He confounds reason with reasoning—that is, he emerges the entire faculty or modus operandi, to which we give the name of reason, in that partial exercise of its function to which we give the name of reasoning. He says that, in matters of certainty, such as the proof of any of Euclid’s theorems, the acts by which the mind ascertains the fit coherence of the several links in the chain of reasoning are acts of reason. Granted.

Also, that in weighing probabilities, a similar coherence is similarly verified by reason. Granted—with liberty of comment that these arts of reason, in either of the two cases have, by the approved practice of language, received the name of reasoning.

But he further signifies—that is, he does not expressly affirm, but, with equivalent certification, he implicitly asserts, and inferentially states that, in examining such a proposition as the following:—“What is, is” (an examination to which confessedly no reasoning is attached), the act by which the mind assents to the truth of this statement is not to be described as an act of reason. He adopts a different phraseology, and calls it intuition.

Observe, my objection is not that he invests the idea with this new name, but that he disparages its old one. I do not object to your calling a spade a shovel, under a certain view of its use, but it remains still necessary that you should admit that a spade is, in the full sense of the word, a spade.

Indeed, I will incidentally remark that I suspect the word “intuition” has been a very good addition to our vocabulary, and I suppose its proper import might be represented as follows:—Reason has two modes of his exercise, the one is called reasoning, and the other intuition. Intuition is the decision of reason on one single point; reasoning—a word proper to demonstrative truth—seems to be nothing more than intuition looking not merely at one point, but at several points successively. So that intuition and reasoning would constitute the self-same function of reason, and the difference in their meanings would be solely owing to the difference in the circumstances under which that function is exercised.

Observe, that I am here only venturing to speculate, and am now returning from that digression.

Whether or not Locke is herein psychologically consistent with himself; whether, indeed, his real theory is not that which I have just conjecturally intimated, is another question, which I shall defer to a future occasion; but whether or not he herein opposes the ordinary, prevailing, and inveterate use of language, which is what I am charging him with doing, and whether or not he has justifiable ground for this innovation which I am denying that he has, are points that must be tried by the ordeal of these three considerations. How are we accustomed to speak? How are we accustomed to write? and what sort of a call for changing our customs in either of these particulars is that which constitutes a genuine call to do so?

In regard to the first of these tests, the literature of all sects and parties has been accustomed to assert that, both in matters of science and of worldly business, reason is the judge of all truth whatever, without exception.

Locke, on the other hand, informs us that reason is the judge of demonstrative truth, of logical truth, of casuistical truth, and of lawyers’ truth, and of these kinds of truth alone, but is not the judge of intuitive or self-evident truth. Our writers would tell us that to deny “what is, is” to be a true statement, would be an offence against reason; but we learn from Locke that reason has no cognisance in this matter, but intuition only has, and consequently that the wrong committed would not be against reason, but against intuition.

Our current speech accords with our literature in this view of the meaning of the word reason; whose efficiency, moreover, it endeavors to amplify, by surrounding it with satellites of adjectives formed from it, the principal of which are “reasonable” and “unreasonable.” Provided with this vocabulary, we pronounce it to be unreasonable to deny any truth whatever that can be well and clearly ascertained; and so far are we from reserving these adjectives for the occasion of demonstrative truth, and holding them inapplicable where self-evident or intuitive truth comes on the carpet, that we account it, if possible, still more unreasonable to deny the latter than the former.

But if the nomenclature adopted by Locke be the right one, there ought to be a change in these current modes of speaking and writing. One who should reject the proofs of Euclid, would be unreasonable; one who should maintain that Thurtel or Greenacre were innocent of murder, would be unreasonable; but, one who should deny the truth of any self-evident proposition, would not be unreasonable; for to say this, would be to say that reason has cognisance of such propositions, whereas, according to him, it is expressly not reason, but intuition that takes this office. The words “intuitional” and “unintuitional,” must be invented to supply the obvious need which the apparent gap discovers; there seems no other way of supplying it.

Lest I should be suspected of somewhat making up a case; of having, perhaps, represented not so much what Locke really means, as what he seems to mean, I will remind the reader that Locke is undertaking the formal definition of a word, and that on such a critical occasion, it is proper to give him credit for not meaning otherwise than he seems to mean.

The passage which is my text, will be found in the earlier part of the seventeenth chapter of the fourth book. Indeed, I could at once prove my indictment by citing a few words from it, accompanied by a comment of my own, had I any right to impose on the reader a belief in the discriminating fairness and matter-of-fact accuracy, both of my extracts and my comment.

I will, however, venture on such a step; I will suppose myself commenting on this passage, and proceed thus: Locke, it will be seen in this, his foremost and professed definition of the word reason, contrasts it with “sense and intuition.”

Whether he holds these to be identical with what he calls “the outward and the inward sense,” is not quite clear. That, however, is not the question.

He says, that these two faculties “reach but a very little way”; for that “the greatest part of our knowledge depends upon deductions and intermediate ideas.” Now, reason, he says, may be defined to be that faculty, whose specific office it is “to find out and apply” those intermediate ideas and deductions by which we obtain knowledge that consists of two kinds, one that which exalts us into “certainty,” the other that which, though less generous diet for the mind, we have constantly good ground for gladly acquiescing in, and which we call “probability.” So that, says Locke, if you ask, “What room is there for the exercise of any other faculty but outward sense and inward perception?” I can abundantly reply, “Very much.” I have shown you that without this “demonstrative” faculty, our knowledge would be but a skeleton; it would, indeed, not be properly speaking knowledge, but mere rudiments of knowledge.

Such is my interpretation of Locke’s definition of reason, in the proper and specific sense of this word. If it is strictly correct, as I believe the intelligent reader will find by reference, then it is Locke confounds reason with reasoning, mistakes a part for the whole, and the whole for a part, and acts similarly—to borrow his own way of illustration—to the representing a gallon to be a quart, or a half-sovereign to be a sovereign.

It is to be observed, too, that it is entirely in behalf of the more showy kind of knowledge, that the mistake is made. The respected name of reason is given exclusively to logic and demonstrating. Good sense, good feeling, just instinct, if they stand alone, have no claim to it; they are put on an inferior footing; true, they are intuition; but what then? they are not reason.

Now, the century introduced by Locke is accused by the present, and it is generally admitted, with some degree of justice, of having “materialistic” tendencies. We may see, then, how Locke’s doctrine, as just described, founded though it is only on nomenclature, hinging merely on definition, incurring whatever wrongness it implicates from no other lapse than that of confounding a word with its derivative, doing nothing, in short, but annul the difference of meaning between the two words, reason and reasoning; we may see how this apparently harmless experiment might tend to supplying these materialistic tendencies with a ground, a rationale, a principle, and thus to exalt their authority, and how, indeed! it just smacks of their spirit.

It may be seen, too, how, from a few slips, such as this on the part of the champion of the “new philosophy,” competing schools of the present age might be able to make up a case, specious enough to gain the acquiescence of a portion of the public against both—with how great futility, I believe, would appear, if the accusations were weighed by a competent tribunal.

And, finally, it might be expected, that the undue exaltation of the demonstrative department of reason, should issue in a reaction into a contrary extreme, and that some Mr. Carlyle might be found to inveigh against “logic,” to sneer at “analysis,” to denounce “cause and effect philosophy” and to praise “mysticism.”

I have already assumed that the third test that I promised, goes against Locke, and requires no examination, simply because he has not advanced it in his behalf. He has assigned no ground for changing the meaning of the word reason, and it is presumable that none is assignable.

The question, What is the Criterion of Truth?—that is, What are the proper means of distinguishing whether anything that is asserted to be true is so or not? claims immediate notice, because such a criterion exists, and the new philosophy necessarily appeals to it when it comes before the public, while it has shown with what effect it can do so, in the case of those of its branches—namely, the purely material and the mathematical, that flourish in society.

Premising that it is a way of certifying truth that has been immemorially used by mankind in their daily affairs, and which they have always, to some extent, instinctively transferred to their judgments in philosophy, and that it is the only possible general and summary criterion of truth, I may describe it as consisting in the unanimous assent to some idea or assertion of all who are thought competent to pronounce concerning it.

Viewed in connection with the thing it verifies, and the parties who use it, the criterion may be thus represented: Any idea, assertion, or opinion, must, by any inquirer, be found true, when he perceives it to be such as would be unanimously assented to by all presumably competent judges of the kind of truth to which it refers.

So that those who use this criterion, and are convinced of the truth of anything through its medium—a proceeding which I have represented as common and habitual to mankind—in thereby pronouncing certain supposed persons to be judges of truth in the said matter, claim themselves to be also judges of it in the matter of so pronouncing. The acts of judgment they thus tacitly challenge to themselves may be said to be to the following effect:—1. They assign the qualifications that constitute competency for a certain function. 2. They decide that there are persons in the community answering to this character. 3. They opine that the view such persons take or would take, imports an assertion of the truth of the idea in question. 4. They accredit that view with being strictly one, supposing that all qualified to arbitrate would acquiesce and agree in the same. 5. They attribute to themselves a similar unanimity. 6. They assume the sufficiency of their own judgment to make all the above conclusions.

These assumptions on their part, so complicated in description, are simple enough in performance. It is plain that mankind—more properly here to be called the public—simply attach themselves to some opinion which they find current in society; while, however, the assumptions I have just described are, in their full measure, but a necessary consequence of their so doing, doubtless their so doing must itself have been dictated by some kind of anticipation of them, but this may, to any degree, have been vague, undetermined, partial, and imperfect.

The rationale of this double bench of judges is thus explained. In reference to almost every kind of truth there is always a certain portion of the community better able to judge than the rest. Hence it becomes clearly the part of the latter, if they wish to be rightly informed, to defer to the opinion of those confessedly better judges—confessed to be such from the general opinion to that effect. Thus a second set of judges perforce, in addition to those that were originally conceived by choice, is implicated in this transaction.

For the primary sort I must seek a name from the French language, which calls them “experts,” the English supplying, I believe, none, except a very vernacular one, the “knowing ones”; the others have already got a well-known name—the public.

The public, in deciding on the occasions in question, what are the qualifications that constitute “experts” may be said to choose them, thereby, however, choosing persons in idea, and not bodily. The relation of the public to these conceptions of theirs is the same as that of the constituencies to the members of Parliament, in the point of one being the choosers and the others the chosen, with a common object in view.

I suppose, to stop the current of my discourse, and adjourn its topic, for the sake of at once bringing the general principle discussed to the test of exemplification, would have its want of logical harmony excused by its being desiderated by the reader.

I had undertaken to prove that this principle—which, for distinction’s sake, I will call the unanimity principle—is the proper and only criterion of scientific truth to the great non-scientific world, and consequently that modern philosophy necessarily appeals to it when it comes before the public. What I had thus taken upon myself to do, obviously was—first, to display and explicate the principle by definition, and this I had already done; and next—to describe it theoretically by showing its manner of existing, and this I was engaged in doing. Leaving this inquiry in the midst, I am now going to deviate into the practical phase of its description, by showing, not how it is, but how it acts. This seems necessary for the satisfaction of the reader, as being the only way of securing him from any, even were it but temporary, misapprehension as to the working value of the principle for which his attention is demanded. I therefore select the six following examples, the two first homely, and the four last philosophical, of its ordinary use by the public.

They will be at once seen to justify my assertion of its having for its main characteristics the two facts—first, that mankind habitually use it, and have always done so; and next, that propositions thus warranted are universally accepted as established truth, and that no one thinks of calling them in question.

1. Thus no one doubts, when coming to the intersection of two roads, he sees a sign-post, on one of whose pointers is written “To London,” and on the other “To Windsor,” no one hesitates to believe that the information thus conveyed to him is true; because he is aware that those who give it are competent to do so, and that none similarly competent will gainsay it.

2. Again, no one doubts that the sun rises and sets once in every twenty-four hours; no one doubts that he so rose and set yesterday. Every one is ready to affirm the certainty of these two facts, but very few can do so, in any great degree, from their own experience; but they help the lack of this by that of their neighbors. Neither is it necessary that they should have any near, nor even the most remote, idea of the personality of those on whose testimony they thus implicitly rely; it suffices they are sure, whoever they may be, they have the right qualifications for testifying in the way they do, and that no one so qualified can contradict their evidence, or dream of doing so.

The above are examples of the criterion of truth, applied to the ideas and proceedings of ordinary life. It will be seen therefrom, first that mankind have in all ages been educated in an acceptance of its principle, according to my definition of it, the principle, namely, of an indubitable certainty of truth, resulting from the unanimous assent to some idea of all who are thought by self and neighbors competent to pronounce thereon; possibly too they may be said to have been educated in some imperfect theoretical appreciation of this principle.

It will secondly be seen therefrom, that the two kinds of unanimity which I have predicated as essential to the proper use and results of this criterion, an unanimity, namely, on the part of the supposed good judges of certain descriptions of truth, who may be called the adepts or knowing ones imagined by the public; and again an unanimity on the part of the public itself in interpreting and adopting their opinion; it will be seen, I say, that this double unanimity is perfectly attainable, nay, perfectly attained, and that too so extensively, as to constitute a common and familiar occurrence on all manner of occasions of daily life.

I will now give instances of their similar use of it in directing their judgments on philosophical questions.

3. Very few of the public are able to examine the proof of any of the theorems of Euclid, yet there is none of them who would think of seriously doubting the truth of anything contained in that book, the ground of their confidence being solely their knowledge of the fact, that the learned in these matters have unanimously so decided.

Every one, again, believes in certain facts that are asserted by navigators, explorers, and geographers, respecting the existence, position, and products of various countries of the globe. Every one, further, believes in certain deductions derived from these facts by naturalists, geologists, astronomers, and so forth. The belief is owing to the unanimous testimony of all these confessedly competent authorities; but whenever they are seen to differ among themselves, the public withholds its entire belief, and either doubts or disbelieves the things asserted. Thus the public is at this day doubtful and divided whether there is such a creature as the sea-serpent. Similarly the public is dubious—for it must needs be so if any section of it is so—whether a certain explorer who was authoritatively sent out about a dozen years ago conjointly by the French Government and Institute, was, in any degree, justified in bringing home the account he did of there being a tribe of men in the interior of Africa having tails, whether this unexpected information is, in any important particular, true.

The two last examples have been furnished by material science. I will now draw one from the other department, with the view of indicating that in non-material science also, numerous propositions circulate among the public that are franked by the same principle to pass as undoubted truth. Such is the maxim of heathen philosophy, recorded by Cicero in his “Officiis”: “Do not to another what you would not he should do to you”; or the same maxim, in its modified form, as given in the New Testament, with the characteristic omission of the negative. The truth of this moral maxim is universally admitted, because it is supposed that no person of presumable moral judgment has ever been known to call it in question.

It would seem, then, that this criterion of truth is—what confessedly, or from easy proof, it is predicable that no other criterion of truth is—a general criterion of truth. I will, however, restrict this pretension to the statement—to be hereafter more largely explained—that it is a general criterion of truth to the public as such, to the public considered as a public; for, indeed, it is not properly usable at all by anyone except in the character of a member of the public. This means that it is a general criterion of truth in the following way: it is applicable to the verification of all truth, so far as it admits of being verified before the public, and made the common property of the community.

6. For even where at first sight you might think it most out of place, I mean in relation to that kind of truth whose primary evidence is the consciousness of the individual, so that the competent witness of truth is necessarily but one person, there is oneness of opinion, there is unanimity, and the testimony of the one competent witness is not contradicted or doubted by that of any other presumably competent. When, for instance, I am conscious of the sensation of seeing an inkstand before me, no one seeing reason to doubt my assertion to that effect, all presumably competent testimony on the subject must needs be concentrated in myself; and the fact of my seeing an inkstand, though for my own conviction verified in a way independent of any such argument, is, for the conviction of others, only pronounceable as true, because all presumably competent authority is of one mind in alleging its truth.

In thus far exemplifying the use of this principle, I have exhibited it in the exercise of its primary office only, which, however, is not that which, on behalf of philosophy, I am here demanding from it. I have shown it, namely, as used by the public to establish truth positively, and not in the way wherein it may be used to distinguish truth comparatively.

But it is solely in this latter office that it becomes a criterion of truth, an arbiter between the true and the false, an indicator of both, and more especially of what has the character of ascertained truth, and what has not; and this, it will be remembered, was the office I sought from it, and constituted the ultimate purpose of my taking up the consideration of the subject.

Having with as much brevity as just suffices for that purpose, explained the nature of the principle in question, and its use by society at large, it now only remains that I should explain that purpose itself, by theory and example.

What I am doing in tracing the unanimity principle from its first instinctive use by the public to its secondary and meditated one by philosophy, is a purely critical act, comparable to that of the rhetorician who appreciates the character of certain modes of thinking which have long since been practised by mankind, and shows what therein is approvable—all the rest being liable to censure.

It was the universal conviction of European Christendom, during many centuries, that the Church, which was popularly supposed to be represented by the Pope, enjoyed peculiarly a divine guidance which made it an infallible judge of truth. This idea was thought to be warranted by the unanimous assent of all right-minded persons, and the denial of it to be the mark of a reprobate spirit, as well as contrary to common sense. We now know the entire futility of this assumption, and that the heretics were not inferior to the orthodox in the power of judging such subjects. Hence in discussing the unanimity principle the question presents itself, How came the public thus wrongly to apply it? What error did they commit in so doing? When the revival of learning and the consequent rise of Protestantism had exposed the error in that form of it, it was still continued under the new social regimes; so that even Locke, the boldest advocate of the rights of man that was tolerated even in his time, stigmatised the dissentients from certain Protestant tenets in the same unjust way that Popery had done to the dissentients from certain Popish ones; speaking of them in two or three places of his essay as persons at once notoriously disreputable in character and weak in intellect; consistently with which estimate he came to the conclusion that the reigning theology was established truth, as being accredited by all those whose opinion was worth taking account of.

Later times have again manifested the futility of the assumption against the new race of dissentients. No one will say that Goethe and Neibuhr (to mention only two) must count for nothing on questions wherein they were as likely to be well informed as their opponents. So that Locke’s side, instead of being warranted by the decisive verdict he imagines, is but one of two suitors in an undetermined cause, neither having yet attracted the votes of the whole jury, and neither consequently yet occupying the position of ascertained truth. Giving everyone a fair hearing is that trial and test of competency which yields the only means of learning who said competent judges are.

A little consideration, even in Locke’s time of less advanced thought, might have informed an intelligent mind, if free from prejudice, that mere prohibitory laws must be of themselves less adverse to the free expression of people’s sentiments than that averted state of the public mind of which they are one of the symptoms. Both from theory and experience we may collect that very much the same laws of supply and demand obtain in matters of opinion as in those of food and raiment; the tongue and the pen, and the previous thought by which these are instructed, must evidently hold back from offering to the public, nay, in a great measure from suggesting to the agent himself, any such ideas as they know the public will not, and must confine themselves to putting forth such only as they suppose it will understand, appreciate, and regard.