I.2.2. Appendix to the Dialectic: The Regulative Employment of the Ideas

The outcome of all dialectical attempts of pure reason does not merely confirm what we have already proved in the Transcendental Analytic, namely, that all those conclusions of ours which profess to lead us beyond the field of possible experience are deceptive and without foundation; it likewise teaches us this further lesson, that human reason has a natural tendency to transgress these limits, and that transcendental ideas are just as natural to it as the categories are to understanding—though with this difference, that while the categories lead to truth, that is, to the conformity of our concepts with the object, the ideas produce what, though a mere illusion, is none the less irresistible, and the harmful influence of which we can barely succeed in neutralising even by means of the severest criticism.

Everything that has its basis in the nature of our powers must be appropriate to, and consistent with, their right employment—if only we can guard against a certain misunderstanding and so can discover the proper direction of these powers. We are entitled, therefore, to suppose that transcendental ideas have their own good, proper, and therefore immanent use, although, when their meaning is misunderstood, and they are taken for concepts of real things, they become transcendent in their application and for that very reason can be delusive. For it is not the idea in itself, but its use only, that can be either transcendent or immanent (that is, either range beyond all possible experience or find employment within its limits), according as it is applied to an object which is supposed to correspond to it, or is directed solely to the use of understanding in general, in respect of those objects that fall to be dealt with by the understanding. All errors of subreption are to be ascribed to a defect of judgment, never to understanding or to reason.

Reason is never in immediate relation to an object, but only to the understanding; and it is only through the understanding that it has its own [specific] empirical employment. It does not, therefore, create concepts (of objects) but only orders them, and gives them that unity which they can have only if they be employed in their widest possible application, that is, with a view to obtaining totality in the various series. The understanding does not concern itself with this totality, but only with that connection through which, in accordance with concepts, such series of conditions come into being. Reason has, therefore, as its sole object, the understanding and its effective application. Just as the understanding unifies the manifold in the object by means of concepts, so reason unifies the manifold of concepts by means of ideas, positing a certain collective unity as the goal of the activities of the understanding, which otherwise are concerned solely with distributive unity.

I accordingly maintain that transcendental ideas never allow of any constitutive employment. When regarded in that mistaken manner, and therefore as supplying concepts of certain objects, they are but pseudo-rational, merely dialectical concepts. On the other hand, they have an excellent, and indeed indispensably necessary, regulative employment, namely, that of directing the understanding towards a certain goal upon which the routes marked out by all its rules converge, as upon their point of intersection. This point is indeed a mere idea, a focus imaginarius, from which, since it lies quite outside the bounds of possible experience, the concepts of the understanding do not in reality proceed; none the less it serves to give to these concepts the greatest [possible] unity combined with the greatest [possible] extension. Hence arises the illusion that the lines have their source in a real object lying outside the field of empirically possible knowledge just as objects reflected in a mirror are seen as behind it. Nevertheless this illusion (which need not, however, be allowed to deceive us) is indispensably necessary if we are to direct the understanding beyond every given experience (as part of the sum of possible experience), and thereby to secure its greatest possible extension, just as, in the case of mirror-vision, the illusion involved is indispensably necessary if, besides the objects which lie before our eyes, we are also to see those which lie at a distance behind our back.

If we consider in its whole range the knowledge obtained for us by the understanding, we find that what is peculiarly distinctive of reason in its attitude to this body of knowledge, is that it prescribes and seeks to achieve its systematisation, that is, to exhibit the connection of its parts in conformity with a single principle. This unity of reason always presupposes an idea, namely, that of the form of a whole of knowledge—a whole which is prior to the determinate knowledge of the parts and which contains the conditions that determine a priori for every part its position and relation to the other parts. This idea accordingly postulates a complete unity in the knowledge obtained by the understanding, by which this knowledge is to be not a mere contingent aggregate, but a system connected according to necessary laws. We may not say that this idea is a concept of the object, but only of the thoroughgoing unity of such concepts, in so far as that unity serves as a rule for the understanding. These concepts of reason are not derived from nature; on the contrary, we interrogate nature in accordance with these ideas, and consider our knowledge as defective so long as it is not adequate to them. By general admission, pure earth, pure water, pure air, etc., are not to be found. We require, however, the concepts of them (though, in so far as their complete purity is concerned, they have their origin solely in reason) in order properly to determine the share which each of these natural causes has in producing appearances. Thus in order to explain the chemical interactions of bodies in accordance with the idea of a mechanism, every kind of matter is reduced to earths (qua mere weight), to salts and inflammable substances (qua force), and to water and air as vehicles (machines, as it were, by which the first two produce their effects). The modes of expression usually employed are, indeed, somewhat different; but the influence of reason on the classifications of the natural scientist is still easily detected.

If reason is a faculty of deducing the particular from the universal, and if the universal is already certain in itself and given, only judgment is required to execute the process of subsumption, and the particular is thereby determined in a necessary manner. This I shall entitle the apodeictic use of reason. If, however, the universal is admitted as problematic only, and is a mere idea, the particular is certain, but the universality of the rule of which it is a consequence is still a problem. Several particular instances, which are one and all certain, are scrutinised in view of the rule, to see whether they follow from it. If it then appears that all particular instances which can be cited follow from the rule, we argue to its universality, and from this again to all particular instances, even to those which are not themselves given. This I shall entitle the hypothetical employment of reason.

The hypothetical employment of reason, based upon ideas viewed as problematic concepts, is not, properly speaking, constitutive, that is, it is not of such a character that, judging in all strictness, we can regard it as proving the truth of the universal rule which we have adopted as hypothesis. For how are we to know all the possible consequences which, as actually following from the adopted principle, prove its universality? The hypothetical employment of reason is regulative only; its sole aim is, so far as may be possible, to bring unity into the body of our detailed knowledge, and thereby to approximate the rule to universality.

The hypothetical employment of reason has, therefore, as its aim the systematic unity of the knowledge of understanding, and this unity is the criterion of the truth of its rules. The systematic unity (as a mere idea) is, however, only a projected unity, to be regarded not as given in itself, but as a problem only. This unity aids us in discovering a principle for the understanding in its manifold and special modes of employment, directing its attention to cases which are not given, and thus rendering it more coherent.

But the only conclusion which we are justified in drawing from these considerations is that the systematic unity of the manifold knowledge of understanding, as prescribed by reason, is a logical principle. Its function is to assist the understanding by means of ideas, in those cases in which the understanding cannot by itself establish rules, and at the same time to give to the numerous and diverse rules of the understanding unity or system under a single principle, and thus to secure coherence in every possible way. But to say that the constitution of the objects or the nature of the understanding which knows them as such, is in itself determined to systematic unity, and that we can in a certain measure postulate this unity a priori, without reference to any such special interest of reason, and that we are therefore in a position to maintain that knowledge of the understanding in all its possible modes (including empirical knowledge) has the unity required by reason, and stands under common principles from which all its various modes can, in spite of their diversity, be deduced—that would be to assert a transcendental principle of reason, and would make the systematic unity necessary, not only subjectively and logically, as method, but objectively also.

We may illustrate this by an instance of the employment of reason. Among the various kinds of unity which conform to the concepts of the understanding, is that of the causality of a substance, which is called power. The various appearances of one and the same substance show at first sight so great a diversity, that at the start we have to assume just as many different powers as there are different effects. For instance, in the human mind we have sensation, consciousness, imagination, memory, wit, power of discrimination, pleasure, desire, etc. Now there is a logical maxim which requires that we should reduce, so far as may be possible, this seeming diversity, by comparing these with one another and detecting their hidden identity. We have to enquire whether imagination combined with consciousness may not be the same thing as memory, wit, power of discrimination, and perhaps even identical with understanding and reason. Though logic is not capable of deciding whether a fundamental power actually exists, the idea of such a power is the problem involved in a systematic representation of the multiplicity of powers. The logical principle of reason calls upon us to bring about such unity as completely as possible; and the more the appearances of this and that power are found to be identical with one another, the more probable it becomes that they are simply different manifestations of one and the same power, which may be entitled, relatively to the more specific powers, the fundamental power. The same is done with the other powers.

The relatively fundamental powers must in turn be compared with one another, with a view to discovering their harmony, and so to bring them nearer to a single radical, that is, absolutely fundamental, power. But this unity of reason is purely hypothetical. We do not assert that such a power must necessarily be met with, but that we must seek it in the interests of reason, that is, of establishing certain principles for the manifold rules which experience may supply to us. We must endeavour, wherever possible, to bring in this way systematic unity into our knowledge.

On passing, however, to the transcendental employment of understanding, we find that this idea of a fundamental power is not treated merely as a problem for the hypothetical use of reason, but claims to have objective reality, as postulating the systematic unity of the various powers of a substance, and as giving expression to an apodeictic principle of reason. For without having made any attempt to show the harmony of these various powers, nay, even after all attempts to do so have failed, we yet presuppose that such a unity does actually exist, and this not only, as in the case cited, on account of the unity of the substance, but also in those cases in which, as with matter in general, we encounter powers which, though to a certain extent homogeneous, are likewise diverse. In all such cases reason presupposes the systematic unity of the various powers, on the ground that special natural laws fall under more general laws, and that parsimony in principles is not only an economical requirement of reason, but is one of nature’s own laws.

It is, indeed, difficult to understand how there can be a logical principle by which reason prescribes the unity of rules, unless we also presuppose a transcendental principle whereby such a systematic unity is a priori assumed to be necessarily inherent in the objects. For with what right can reason, in its logical employment, call upon us to treat the multiplicity of powers exhibited in nature as simply a disguised unity, and to derive this unity, so far as may be possible, from a fundamental power—how can reason do this, if it be free to admit as likewise possible that all powers may be heterogeneous, and that such systematic unity of derivation may not be in conformity with nature? Reason would then run counter to its own vocation, proposing as its aim an idea quite inconsistent with the constitution of nature. Nor can we say that reason, while proceeding in accordance with its own principles, has arrived at knowledge of this unity through observation of the accidental constitution of nature. The law of reason which requires us to seek for this unity, is a necessary law, since without it we should have no reason at all, and without reason no coherent employment of the understanding, and in the absence of this no sufficient criterion of empirical truth. In order, therefore, to secure an empirical criterion we have no option save to presuppose the systematic unity of nature as objectively valid and necessary.

Although philosophers have not always acknowledged this transcendental principle, even to themselves, or indeed been conscious of employing it, we none the less find it covertly implied, in remarkable fashion, in the principles upon which they proceed. That the manifold respects in which individual things differ do not exclude identity of species, that the various species must be regarded merely as different determinations of a few genera, and these, in turn, of still higher genera, and so on; in short, that we must seek for a certain systematic unity of all possible empirical concepts, in so far as they can be deduced from higher and more general concepts—this is a logical principle, a rule of the Schools, without which there could be no employment of reason. For we can conclude from the universal to the particular, only in so far as universal properties are ascribed to things as being the foundation upon which the particular properties rest.

That such unity is to be found in nature, is presupposed by philosophers in the well-known scholastic maxim, that rudiments or principles must not be unnecessarily multiplied (entia praeter necessitatem non esse multiplicanda). This maxim declares that things by their very nature supply material for the unity of reason, and that the seemingly infinite variety need not hinder us from assuming that behind this variety there is a unity of fundamental properties—properties from which the diversity can be derived through repeated determination. This unity, although it is a mere idea, has been at all times so eagerly sought, that there has been need to moderate the desire for it, not to encourage it. A great advance was made when chemists succeeded in reducing all salts to two main genera, acids and alkalies; and they endeavour to show that even this difference is merely a variety, or diverse manifestation, of one and the same fundamental material. Chemists have sought, step by step, to reduce the different kinds of earths (the material of stones and even of metals) to three, and at last to two; but, not content with this, they are unable to banish the thought that behind these varieties there is but one genus, nay, that there may even be a common principle for the earths and the salts. It might be supposed that this is merely an economical contrivance whereby reason seeks to save itself all possible trouble, a hypothetical attempt, which, if it succeeds, will, through the unity thus attained, impart probability to the presumed principle of explanation. But such a selfish purpose can very easily be distinguished from the idea. For in conformity with the idea everyone presupposes that this unity of reason accords with nature itself, and that reason—although indeed unable to determine the limits of this unity—does not here beg but command.

If among the appearances which present themselves to us, there were so great a variety—I do not say in form, for in that respect the appearances might resemble one another; but in content, that is, in the manifoldness of the existing entities—that even the acutest human understanding could never by comparison of them detect the slightest similarity (a possibility which is quite conceivable), the logical law of genera would have no sort of standing; we should not even have the concept of a genus, or indeed any other universal concept; and the understanding itself, which has to do solely with such concepts, would be non-existent. If, therefore, the logical principle of genera is to be applied to nature (by which I here understand those objects only which are given to us), it presupposes a transcendental principle. And in accordance with this latter principle, homogeneity is necessarily presupposed in the manifold of possible experience (although we are not in a position to determine in a priori fashion its degree); for in the absence of homogeneity, no empirical concepts, and therefore no experience, would be possible.

The logical principle of genera, which postulates identity, is balanced by another principle, namely, that of species, which calls for manifoldness and diversity in things, notwithstanding their agreement as coming under the same genus, and which prescribes to the understanding that it attend to the diversity no less than to the identity. This principle (of discriminative observation, that is, of the faculty of distinction) sets a limit to possible indiscretion in the former principle (of the faculty of wit); and reason thus exhibits a twofold, self-conflicting interest, on the one hand interest in extent (universality) in respect of genera, and on the other hand in content (determinateness) in respect of the multiplicity of the species. In the one case the understanding thinks more under its concepts, in the other more in them. This twofold interest manifests itself also among students of nature in the diversity of their ways of thinking. Those who are more especially speculative are, we may almost say, hostile to heterogeneity, and are always on the watch for the unity of the genus; those, on the other hand, who are more especially empirical, are constantly endeavouring to differentiate nature in such manifold fashion as almost to extinguish the hope of ever being able to determine its appearances in accordance with universal principles.

This latter mode of thought is evidently based upon a logical principle which aims at the systematic completeness of all knowledge—prescribing that, in beginning with the genus, we descend to the manifold which may be contained thereunder, in such fashion as to secure extension for the system, just as in the alternative procedure, that of ascending to the genus, we endeavour to secure the unity of the system. For if we limit our attention to the sphere of the concept which marks out a genus, we can no more determine how far it is possible to proceed in the [logical] division of it, than we can judge merely from the space which a body occupies how far it is possible to proceed in the [physical] division of its parts. Consequently, every genus requires diversity of species, and these in turn diversity of subspecies; and since no one of these subspecies is ever itself without a sphere (extent as conceptus communis), reason, in being carried to completion, demands that no species be regarded as being in itself the lowest. For since the species is always a concept, containing only what is common to different things, it is not completely determined. It cannot, therefore, be directly related to an individual, and other concepts, that is, subspecies, must always be contained under it. This law of specification can be formulated as being the principle: entium varietates non temere esse minuendas.

But it is easily seen that this logical law would be without meaning and application if it did not rest upon a transcendental law of specification, which does not indeed demand an actual infinity of differences in the things which can be objects to us—the logical principle, as affirming only the indeterminateness of the logical sphere in respect of possible division, gives no occasion for any such assertion—but which none the less imposes upon the understanding the obligation of seeking under every discoverable species for subspecies, and under every difference for yet smaller differences. For if there were no lower concepts, there could not be higher concepts. Now the understanding can have knowledge only through concepts, and therefore, however far it carries the process of division, never through mere intuition, but always again through lower concepts. The knowledge of appearances in their complete determination, which is possible only through the understanding, demands an endless progress in the specification of our concepts, and an advance to yet other remaining differences, from which we have made abstraction in the concept of the species, and still more so in that of the genus.

This law of specification cannot be derived from experience, which can never open to our view any such extensive prospects. Empirical specification soon comes to a stop in the distinction of the manifold, if it be not guided by the antecedent transcendental law of specification, which, as a principle of reason, leads us to seek always for further differences, and to suspect their existence even when the senses are unable to disclose them. That absorbent earths are of different kinds (chalk and muriatic earths), is a discovery that was possible only under the guidance of an antecedent rule of reason—reason proceeding on the assumption that nature is so richly diversified that we may presume the presence of such differences, and therefore prescribing to the understanding the task of searching for them. Indeed it is only on the assumption of differences in nature, just as it is also only under the condition that its objects exhibit homogeneity, that we can have any faculty of understanding whatsoever. For the diversity of that which is comprehended under a concept is precisely what gives occasion for the employment of the concept and the exercise of the understanding.

Reason thus prepares the field for the understanding: (1) through a principle of the homogeneity of the manifold under higher genera; (2) through a principle of the variety of the homogeneous under lower species; and (3) in order to complete the systematic unity, a further law, that of the affinity of all concepts—a law which prescribes that we proceed from each species to every other by gradual increase of the diversity. These we may entitle the principles of homogeneity, specification, and continuity of forms. The last named arises from union of the other two, inasmuch as only through the processes of ascending to the higher genera and of descending to the lower species do we obtain the idea of systematic connection in its completeness. For all the manifold differences are then related to one another, inasmuch as they one and all spring from one highest genus, through all degrees of a more and more widely extended determination.

The systematic unity, prescribed by the three logical principles, can be illustrated in the following manner. Every concept may be regarded as a point which, as the station for an observer, has its own horizon, that is, a variety of things which can be represented, and, as it were, surveyed from that standpoint. This horizon must be capable of containing an infinite number of points, each of which has its own narrower horizon; that is, every species contains subspecies, according to the principle of specification, and the logical horizon consists exclusively of smaller horizons (subspecies), never of points which possess no extent (individuals). But for different horizons, that is, genera, each of which is determined by its own concept, there can be a common horizon, in reference to which, as from a common centre, they can all be surveyed; and from this higher genus we can proceed until we arrive at the highest of all genera, and so at the universal and true horizon, which is determined from the standpoint of the highest concept, and which comprehends under itself all manifoldness—genera, species, and subspecies.

We are carried to this highest standpoint by the law of homogeneity, and to all lower standpoints, and their greatest possible variety, by the law of specification. And since there is thus no void in the whole sphere of all possible concepts, and since nothing can be met with outside this sphere, there arises from the presupposition of this universal horizon and of its complete division, the principle: non datur vacuum formarum, that is, that there are not different, original, first genera, which are isolated from one another, separated, as it were, by an empty intervening space; but that all the manifold genera are simply divisions of one single highest and universal genus. From this principle there follows, as its immediate consequence: datur continuum formarum, that is, that all differences of species border upon one another, admitting of no transition from one to another per saltum, but only through all the smaller degrees of difference that mediate between them. In short, there are no species or subspecies which (in the view of reason) are the nearest possible to each other; still other intermediate species are always possible, the difference of which from each of the former is always smaller than the difference between these.

The first law thus keeps us from resting satisfied with an excessive number of different original genera, and bids us pay due regard to homogeneity; the second, in turn, imposes a check upon this tendency towards unity, and insists that before we proceed to apply a universal concept to individuals we distinguish subspecies within it. The third law combines these two laws by prescribing that even amidst the utmost manifoldness we observe homogeneity in the gradual transition from one species to another, and thus recognise a relationship of the different branches, as all springing from the same stem.

This logical law of the continuum specierum (formarum logicarum) presupposes, however, a transcendental law (lex continui in natura), without which the former law would only lead the understanding astray, causing it to follow a path which is perhaps quite contrary to that prescribed by nature itself. This law must therefore rest upon pure transcendental, not on empirical, grounds. For if it rested on empirical grounds, it would come later than the systems, whereas in actual fact it has itself given rise to all that is systematic in our knowledge of nature. The formulation of these laws is not due to any secret design of making an experiment, by putting them forward as merely tentative suggestions. Such anticipations, when confirmed, yield strong evidence in support of the view that the hypothetically conceived unity is well-grounded; and such evidence has therefore in this respect a certain utility. But it is evident that the laws contemplate the parsimony of fundamental causes, the manifoldness of effects, and the consequent affinity of the parts of nature as being in themselves in accordance both with reason and with nature. Hence these principles carry their recommendation directly in themselves, and not merely as methodological devices.

But it is easily seen that this continuity of forms is a mere idea, to which no congruent object can be discovered in experience. For in the first place, the species in nature are actually divided, and must therefore constitute a quantum discretum. Were the advance in the tracing of their affinity continuous, there would be a true infinity of intermediate members between any two given species, which is impossible. And further, in the second place, we could not make any determinate empirical use of this law, since it instructs us only in quite general terms that we are to seek for grades of affinity, and yields no criterion whatsoever as to how far, and in what manner, we are to prosecute the search for them.

If we place these principles of systematic unity in the order appropriate to their empirical employment, they will stand thus: manifoldness, affinity, unity each being taken, as an idea, in the highest degree of its completeness. Reason presupposes the knowledge which is obtained by the understanding and which stands in immediate relation to experience, and seeks for the unity of this knowledge in accordance with ideas which go far beyond all possible experience. The affinity of the manifold (as, notwithstanding its diversity, coming under a principle of unity) refers indeed to things, but still more to their properties and powers. Thus, for instance, if at first our imperfect experience leads us to regard the orbits of the planets as circular, and if we subsequently detect deviations therefrom, we trace the deviations to that which can change the circle, in accordance with a fixed law, through all the infinite intermediate degrees, into one of these divergent orbits. That is to say, we assume that the movements of the planets which are not circular will more or less approximate to the properties of a circle; and thus we come upon the idea of an ellipse. Since the comets do not, so far as observation reaches, return in any such courses, their paths exhibit still greater deviations. What we then do is to suppose that they proceed in a parabolic course, which is akin to the ellipse, and which in all our observations is indistinguishable from an ellipse that has its major axis indefinitely extended. Thus, under the guidance of these principles, we discover a unity in the generic forms of the orbits, and thereby a unity in the cause of all the laws of planetary motion, namely, gravitation. And we then extend our conquests still further, endeavouring to explain by the same principle all variations and seeming departures from these rules; finally, we even go on to make additions such as experience can never confirm, namely, to conceive, in accordance with the rules of affinity, hyperbolic paths of comets, in the course of which these bodies entirely leave our solar system, and passing from sun to sun, unite the most distant parts of the universe—a universe which, though for us unlimited, is throughout held together by one and the same moving force.

The remarkable feature of these principles, and what in them alone concerns us, is that they seem to be transcendental, and that although they contain mere ideas for the guidance of the empirical employment of reason—ideas which reason follows only as it were asymptotically, i.e. ever more closely without ever reaching them—they yet possess, as synthetic a priori propositions, objective but indeterminate validity, and serve as rules for possible experience. They can also be employed with great advantage in the elaboration of experience, as heuristic principles. A transcendental deduction of them cannot, however, be effected; in the case of ideas, as we have shown above, such a deduction is never possible.

In the Transcendental Analytic we have distinguished the dynamical principles of the understanding, as merely regulative principles of intuition, from the mathematical, which, as regards intuition, are constitutive. None the less these dynamical laws are constitutive in respect of experience, since they render the concepts, without which there can be no experience, possible a priori. But principles of pure reason can never be constitutive in respect of empirical concepts; for since no schema of sensibility corresponding to them can ever be given, they can never have an object in concreto. If, then, we disallow such empirical employment of them, as constitutive principles, how are we to secure for them a regulative employment, and therewith some sort of objective validity, and what can we mean by such regulative employment?

The understanding is an object for reason, just as sensibility is for the understanding. It is the business of reason to render the unity of all possible empirical acts of the understanding systematic; just as it is of the understanding to connect the manifold of the appearances by means of concepts, and to bring it under empirical laws. But the acts of the understanding are, without the schemata of sensibility, undetermined; just as the unity of reason is in itself undetermined as regards the conditions under which, and the extent to which, the understanding ought to combine its concepts in systematic fashion. But although we are unable to find in intuition a schema for the complete systematic unity of all concepts of the understanding, an analogon of such a schema must necessarily allow of being given. This analogon is the idea of the maximum in the division and unification of the knowledge of the understanding under one principle. For what is greatest and absolutely complete can be determinately thought, all restricting conditions, which give rise to an indeterminate manifoldness, being left aside. Thus the idea of reason is an analogon of a schema of sensibility; but with this difference, that the application of the concepts of the understanding to the schema of reason does not yield knowledge of the object itself (as is the case in the application of categories to their sensible schemata), but only a rule or principle for the systematic unity of all employment of the understanding. Now since every principle which prescribes a priori to the understanding thoroughgoing unity in its employment, also holds, although only indirectly, of the object of experience, the principles of pure reason must also have objective reality in respect of that object, not, however, in order to determine anything in it, but only in order to indicate the procedure whereby the empirical and determinate employment of the understanding can be brought into complete harmony with itself. This is achieved by bringing its employment, so far as may be possible, into connection with the principle of thoroughgoing unity, and by determining its procedure in the light of this principle.

I entitle all subjective principles which are derived, not from the constitution of an object but from the interest of reason in respect of a certain possible perfection of the knowledge of the object, maxims of reason. There are therefore maxims of speculative reason, which rest entirely on its speculative interest, although they may seem to be objective principles.

When merely regulative principles are treated as constitutive, and are therefore employed as objective principles, they may come into conflict with one another. But when they are treated merely as maxims, there is no real conflict, but merely those differences in the interest of reason that give rise to differing modes of thought. In actual fact, reason has only one single interest, and the conflict of its maxims is only a difference in, and a mutual limitation of, the methods whereby this interest endeavours to obtain satisfaction.

Thus one thinker may be more particularly interested in manifoldness (in accordance with the principle of specification), another thinker in unity (in accordance with the principle of aggregation). Each believes that his judgment has been arrived at through insight into the object, whereas it really rests entirely on the greater or lesser attachment to one of the two principles. And since neither of these principles is based on objective grounds, but solely on the interest of reason, the title ‘principles’ is not strictly applicable; they may more fittingly be entitled ‘maxims’. When we observe intelligent people disputing in regard to the characteristic properties of men, animals, or plants—even of bodies in the mineral realm—some assuming, for instance, that there are certain special hereditary characteristics in each nation, certain well-defined inherited differences in families, races, etc., whereas others are bent upon maintaining that in all such cases nature has made precisely the same provision for all, and that it is solely to external accidental conditions that the differences are due, we have only to consider what sort of an object it is about which they are making these assertions, to realise that it lies too deeply hidden to allow of their speaking from insight into its nature. The dispute is due simply to the twofold interest of reason, the one party setting its heart upon, or at least adopting, the one interest, and the other party the other. The differences between the maxims of manifoldness and of unity in nature thus easily allow of reconciliation. So long, however, as the maxims are taken as yielding objective insight, and until a way has been discovered of adjusting their conflicting claims, and of satisfying reason in that regard, they will not only give rise to disputes but will be a positive hindrance, and cause long delays in the discovery of truth.

Similar observations are relevant in regard to the assertion or denial of the widely discussed law of the continuous gradation of created beings, which was propounded by Leibniz, and admirably supported by Bonnet. It is simply the following out of that principle of affinity which rests on the interest of reason. For observation and insight into the constitution of nature could never justify us in the objective assertion of the law. The steps of this ladder, as they are presented to us in experience, stand much too far apart; and what may seem to us small differences are usually in nature itself such wide gaps, that from any such observations we can come to no decision in regard to nature’s ultimate design—especially if we bear in mind that in so great a multiplicity of things there can never be much difficulty in finding similarities and approximations. On the other hand, the method of looking for order in nature in accordance with such a principle, and the maxim which prescribes that we regard such order—leaving, however, undetermined where and how far—as grounded in nature as such, is certainly a legitimate and excellent regulative principle of reason. In this regulative capacity it goes far beyond what experience or observation can verify; and though not itself determining anything, yet serves to mark out the path towards systematic unity.