Theory and History of Ontology

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Christian Wolff's Ontology: Existence as "Complement of Possibility"


"Let us open Wolff's Ontology and read his Preface: "Prime Philosophy (namely, metaphysics) was first laden by the Scholastics with enviable praise, but, ever after the success of Cartesian philosophy, it fell into disrepute and has become a laughing stock to all." (10) What Wolff clearly sees then is that, since the time when Descartes "grew weary of metaphysics," there still may have been metaphysicians, but there has been no metaphysics. As a distinct science, metaphysics has simply ceased to be. And Kant himself was only echoing Wolff when he wrote in his Preface to the first edition of the Critique of Pure Reason: "There was a time when metaphysics used to be called the queen of sciences ... Now, in our own century, it is quite fashionable to show contempt for it." Our own century here is the eighteenth century, which was the century of both Wolff and Kant.

When he made up his mind to put a stop to that technical decadence in the field of philosophy, Wolff was keenly conscious of carrying on the work of the great Scholastics. What they had done was not perfect, but that was the thing to do, and, since it could be done better, Wolff himself was going to do it all over again. Let us be as precise as possible. Wolff did not wish to be reproached with bringing back a Scholastic philosophy that was dead. In point of fact, that was not what he wanted to do. But he was claiming the right to retain at least Scholastic terminology, for all there was to be done about it was, keeping the same terms, to build up better definitions and more exactly determined propositions. (11)

This is what Wolff set about doing first with the term "being," and it is typical of his attitude that he can reach it only through the notion of possibility. "Being," Wolff says, "is what can exist and, consequently, that with which existence is not incompatible: Ens dicitur quod existere potest, consequenter cui existentia non repugnat. (12) In other words, what is possible is a being: Quod possible est, ens est. (13) Besides, Wolff adds, this is a metaphysical notion which is accepted by all, and which exactly tallies with common language. "Being," "something," "possible;" here are so many words that are practically synonymous, and metaphysics does nothing more than bring their implicit meanings out in the open. True enough, what is commonly called a "being" is something that exists, but he who understands that a A is being because it exists will as easily understand that, if A exists, it is because it can exist.(14) Possibility then is the very root of existence, and this is why the possibles are commonly called beings. The proof of it is that we commonly speak of beings past or future, that is, of beings that no longer exist or that do not yet exist. In any case, their being has nothing to do with actual existence; it is, though a merely possible being, yet a being.

In order to probe more deeply into the knowledge of being, what we have to do is to inquire into the causes of its possibility. The first one is, of course, the one we have already mentioned, namely, the absence of inner contradiction; but this is not enough. In order to posit a being, one must ascribe to its notion such constituent parts as are not only compatible among themselves, but are its primary constituent parts. The primary constituents of a being are those which are neither determined by some element foreign to that being, nor determined by any one of the other constituent elements of the same being. If an element supposedly foreign to some being were determining with respect to any one of those elements which enter its constitution, then it would not be foreign to it; it would be one of its constituent elements. On the other hand, if some of the constituent elements of a being determine each other, then we must retain only the determining elements as constituent parts of that being.(15) In short, every being is made up of such elements as are both compatible and prime. Such elements shall be called the "essentials" of being ( essentialia), because they constitute the very essence. Hence this conclusion, whose full significance it is superfluous to stress: Essence is what is conceived of being in the first place and, without it, being cannot be.(16) Thus, the essence of the equilateral triangle is made up of the number three and of the equality of its sides; again, the essence of virtue is made up of a habit ( habitus) of the will and of the conformity with natural law of the acts which follow from that habit. Let any one of those conditions be altered, there is left neither equilateral triangle nor virtue; let them be all posited, then there is equilateral triangle and virtue. The presence of the "essentials" of the thing is therefore both necessary and sufficient to define its essence. Those "essentials" always entail certain properties which are inseparable from them and, since a thing never is without its "essentials," it is also inseparable from the thing. Such properties are called the "attributes" of being. As to its "modes," they are such ulterior determinations which are neither determined by the essence nor contradictory with it. The attributes of a being are always given with it, but not its modes, which are what the Scholastics used to call "accidents."

In a being so conceived, the "essentials" obviously are the very core of reality. Taken as non-contradictory, they ensure the possibility of being. It is through its "essentials" that a being is possible: Per essentialia ens possibile est. Now, since the essence of being is one with its possibility, he who acknowledges the intrinsic possibility of a thing knows also its essence. We are saying "acknowledges," and rightly so, for it is possible to account for the attributes of being from the "essentials" of that being, but there is no accounting for the fact that those "essentials" belong to it. Since they are prime, there is nothing above them from which they could be deduced. As to the modes, they cannot be deduced from their essence either. For, what makes up an essence accounts for the fact that such and such a mode may belong to a certain being; it does not account for the fact that such a mode actually does belong to it. The reason for the actual presence of modes in a given being must always be looked for outside that being. We call "external" those beings which constitute the sufficient reason for the actual presence, in a given being, of modes which cannot be sufficiently accounted for by its essence alone. The essence then is for any being the sufficient reason for the actual presence of its attributes and of the possible presence of its modes(17) Hence its nominal definition: "Essence is that which is conceived of a being in the first place, and in which is to be found the sufficient reason why all the rest either actually belongs to it or else may belong to it: Essentia definiri potest per id quod primum de ente concipitur et in quo ratio continetur sufficiens, cur caetera vel actu insint, vel finesse possint." (18)

The scrupulously exacting method which Wolff was using in his determination of being was entirely his own, but the results achieved by that method had really nothing new. And Wolff himself was clearly aware of it."

From: Etienne Gilson - Being and some philosophers - Toronto, Pontifical Institute of Mediaeval Studies, 1952 (Second edition corrected and enlarged; first edition 1949) pp. 114-116.

(10) Wolff, Ontologia, beginning of the Preface. Cf.: " Si Cartesius non fastidio philosophiae primue correplus fuisset . . ."

(11) Wolff, Ontologia, n. 12, pp. 4-5

(12) Ibid., n. 134, p. 60

(13) Ibid., n. 135, p. 60

(14) Ibid, n. 139, p. 61

(15) Ibid., n. 142, p. 62

(16) Ibid., n. 144, p. 63

(17) Ibid., n. 167, p. 77

(18) Ibid., n. 168, p. 72

"In Christian Wolff we have a Leibniz purged of poetry, but also purged of some exaggerated conceptions, for example, the drowsy or slumbering monads, and the phenomenal character of space. All is built into an immense, systematic exposition, magnificent in its formal rigour and clarity, and building on, though also improving, the ontological, cosmological, and theological doctrines of the Aristotelian schoolmen and, in particular, of Suárez. (The improvements are possibly due to Platonizing influences, which modified the ingrained love of the individual instance so characteristic of the Aristotelians.) Christian Wolff expounded his systematization both in a German version (the Logic, Metaphysics, Ethics, Politics, Natural Theology, etc.), and also in a Latin version (a Logic (1728), an Ontology (1730), a Cosmology (1731), a Psychology (1732 and 1734), a Natural Theology (1736-7), and a Universal Practical Philosophy (1738-9)). There are also many political writings of interest. To this vast system, with its innumerable Epigonoi -- Bilfinger, Meier, Rüdiger, Baumgarten, Tetens, Crusius, and so on -- Kant made his great emendations, which have been exaggerated into the idealisms, and later the positivisms, by which the thought and even the public policy of Europe has been bemused. What is, however, amazing is the immense volume and solid merit of Wolff's works, and the almost total misunderstanding and neglect that has since enshrouded them, so that copies of Wolffian books are hardly to be found in libraries outside of Germany.


Wolff's Ontology begins (27) with the assertion of the two laws of contradiction and sufficient reason, both fundamental to the assertion that something is, or that it is not. The former requires that what is must be free from inner conflict, the latter that, if it does not, like a necessary being, have a reason for being in its own nature, it must depend on such a reason in something other than itself. The law of causation, as we ordinarily understand it, is for Wolff only a special form of the law of sufficient reason, pertinent to temporal, changeable things and their states (71). From these principles Wolff proceeds to the consideration of the metaphysical modalities, of which the most fundamental is the possible, the negation of the self-contradictory, or logically impossible. Everything actual, he holds, is by the law of contradiction possible, but he here embraces some invalid theorems, for instance, that a possible consequence can only have possible premisses. Obviously, modal logic is still insecure, though Wolff's treatment of apagogic proof in 98 is of some interest. From Wolffian principles it follows that the notion of an entity not wholly determinate is 'imaginary', and that the indeterminate is only what is for us determinable, and that it will have to be determined by a sufficient reason (111, 117). There is no room in Wolffianism, any more than in Leibnizianism, for radical alternativity: Kant, however, will diverge from this position under the influence of Crusius.

All this leads, however, to Wolff's treatment of what he calls an entity: an entity is defined as any thing which can exist, to which existence is not repugnant. Thus warmth in this stone is a something, an entity, since a stone certainly can be warm or a warm stone can exist. There does not need to be any actual stone-warmth for us to have an entity before us. An entity is, however, rightly called fictitious or imaginary, if it lacks existence, which does not, however, make it less of an entity. These near-Meinongian positions are of great contemporary interest, and form the spring-board for much of Kant's later criticisms of the ontological proof, which is Wolffian enough to treat 100 possible dollars as if they certainly vere something. Wolff goes on to draw the distinctions of essential features and attributes, on the one hand, which always must belong to an entity, and its modes, on the other hand, which are merely the characters that it can have and also can not have. Obviously, however, something must be added to possibility to raise it to full existence, and this Wolff is simply content to call the possibility-complement ( 174). It rather resembles the modal moment of Meinong. He proposes to deal with this possibility-complement separately in his discussions of different spheres, for example, theology, cosmology, and psychology, since the intrinsically sufficient reason which makes God an actual existent is not at all like the extrinsically sufficient reason which underlies existence in the cosmological sphere. It is deeply characteristic, and deeply interesting, that Wolff should make actuality a mere enrichment of the possible, not the latter an impoverished abstraction from the former. The efforts of Wittgenstein, Carnap, Ryle, Quine, and so on have shown the hopelessness of trying to elucidate the possible in terms of the actual: the traditional priority may well prove more successful. Both tendencies are of course manifest in Kant's treatments of possibility, the 'modern' in, for example, the Postulates of Empirical Thought, and the Wolffian in many 'transcendental' contexts. Individuation does not, for Wolff, represent a going beyond the possible. It merely occurs where we have the complete determination which the logico-ontological laws require, and there are, accordingly, imaginary and fictitious as well as real ones. The latter may be far more determinate than any characters in fiction, but they will still lack a final nuance of determination. There are, likewise, incompletely determinate specific and generic properties of individuals, all of which must rank among imaginary entities, though some, connected with actual instances, will obviously be less imaginary than others. Wolff has here developed points which Meinong was later to develop in his doctrine of complete and incomplete objects, and there are also many anticipations of the modern theory of possible worlds."

From: John Niemeyer Findlay - Kant and the transcendental object. A Hermeneutic study - Oxford, Clarendon press, 1981, pp. 38-41

"One cannot plunge directly into Wolffian natural theology, however, since it must be viewed within the closely knit context of a certain conception of philosophy and ontology. From Wolff's opening definition of philosophy as 'the science of possibles, in so far as they can be' or have an essential nature, it is evident that his is a system of possibility and essence in which the role of existence is a subordinate one. It is not a totally de-existentialized philosophy; it is one in which knowable and systematically exploitable being primarily means the possible essence and in which existence is admitted only by virtue of some correlation it has with this essence. What does not stand out so clearly is the reason why Wolff settled upon this essentialist viewpoint and yet never totally submerged the distinctive reality of existence.

Part of the explanation comes from Wolff's complex intellectual heritage. He was just as thoroughly familiar with the critical work of the skeptics and empiricists as with the rationalist tradition. The skeptical arguments convinced him of the impossibility of demonstratively defending our knowledge of the existing external world, either through a rationalist deduction or through an empiricist inference. Hence he concluded that it was too risky to base his philosophy upon the thesis of the reality of the material universe; his fundamental definitions remained deliberately neutral about the independent existence of a world corresponding with our ideas. This skeptically generated neutrality inclined him to focus upon the essential and the possible, without making any primary commitments about sensible existents. Nevertheless, the British scientists and philosophers also convinced him of the danger of entirely ignoring the existential aspect.

As a compromise, Wolff calls for a union in holy matrimony of three kinds of human knowledge: historical, philosophical, and mathematical. Historical knowledge means the empirical assurance, gained mainly through sense experience and experiments, that certain things exist or occur. Wolff hails it as the foundation of all philosophy and the constant guide of all inferential reasoning. Yet he wavers between saying that empirical knowledge assures us indubitably that certain things actually do exist and saying that it merely makes us reflectively aware of having the ideas of things that can exist or come to be. This ambiguity about the import of sense experience stems from his basic epistemological neutrality and leads him to depreciate its certainty. Experiential certainty concerns the bare fact (real or ideal) and does not extend to the sufficient reason for the fact. Hence philosophical certainty must be non-experiential in its own proper form. Every ounce of it (to use Wolff's own emphatic phrase) derives from the use of the mathematical method, which risks nothing on the real existent but concentrates upon the determinate quantity of possible objects and essential relations. This method enables philosophy to determine with perfect certainty the reasons why objects may come to be or why being is possible. Hence philosophy is primarily a study of the internal essentialia, or essential components, and the external reasons, or causes of the possibility of these essential components. Existence is studied properly in philosophy only to the extent that it can be drawn out with certainty from the known essential structure.

Wolff never removes the radical dichotomy between empirical and mathematico-philosophical certainties, between knowledge of fact and of possible essence. Their matrimonial bond is not based upon some unifying doctrinal principle but rests solely upon Wolff's personal awareness of the need for both approaches. His desire to found philosophy on an existential basis in experience is blocked by the skeptical critique, and he is thereby forced to locate philosophical certainty in the possible essences and their sufficient reasons. And yet he is also unwilling to follow 'Leibniz in overcoming the distinction between truth's of fact and truths of essence by means of the principle of sufficient reason. Leibniz accords the primacy to this principle, since it expresses the dynamic law of quasi-autonomous essences, to which God must give a consent decree governing His creation of the existing world. For Wolff, however,,the essences are unequivocally grounded in the divine intellect and enjoy no quasi-independence. Hence the principle of sufficient reason can give essential connections or reasons for facts, but it cannot furnish any deductive certitude concerning the actual facts themselves or existential productions of the divine will, There is no objectively determining ground which shapes God's existential decisions and closes the gap in man's philosophical system. Hence the principle of sufficient reason must remain subordinate to the principle of contradiction, which provides an indubitable certainty, at least, about the internal consistency and possibility of the essential traits as such.

In conformity with this view of philosophy, Wolff then defines ontology as the science of being, i.e., of that which can exist or that to which existence is not repugnant. In the main, it is the science of essence, namely, "that which is first of all conceived about being, and in which is contained the sufficient reason why other aspects either actually belong to it or can belong to it." Ontology is a strict science precisely because it confines itself to a general study of being as possible or essentially constituted -- he sphere where a mathematically rigorous certitude is obtainable. Existence figures in ontology either obliquely, as the complement of possibility, or negatively, as the furnisher of a norm of non-repugnance. As the directly known act of a thing, it does not come within the scope of ontology, which remains a nonexistential discipline. Because of the nonexistential character of ontology or general metaphysics, Wolff requires three special parts of metaphysics to determine the principles of the possibility of existence in the three main areas of being. Cosmology studies the reasons of being in the contingent, material world; psychology deduces the soul as the sufficient reason for the existence of mental acts; natural theology demonstrates God as the ground of existence for His own attributes and modes, as well as for the existence of the world. Natural theology presupposes these other sciences. From ontology, it draws its general principles and orientation; from cosmology, a factual basis in the material world; from psychology, a basis in the soul and also some special insight into the spiritual perfections which help us to know God's nature."

From: James Collins - God in Modern Philosophy - Chicago, Henry Regnery Company, 1959, pp. 134-136 (notes omitted)


"Wolff's Ontology is a long, systematic treatise of what had been generally called before him "metaphysics" or "first philosophy." The term 'ontology' to refer to this rather traditional discipline had antecedents before Wolff used it in the title of his book, however. In 1647 Clauvergius [Johannes Clauberg] published a treatise with the title Elementa philosophiae sive ontosophia in which he explicitly argued in favor of a more precise name for what was generally called "metaphysics." The primary reason behind the shift of terminology had to do with the object of study of the discipline, which Clauvergius identified with being in general.(10) Wolff, following suit, titled his book Philosophia prima sive ontologia (1729), defining the subject of study as the science of being in general, that is, of being insofar as it is being.(11)

The Ontology, in comparison with the extensive systematic metaphysical treatises of late Scholastics, is fairly short. It is divided into three sections: a section entitled "Prolegomena" and two parts. The Prolegomena deals with the nature of ontology and of the terms and notions with which it concerns itself. In the first of the two parts into which the rest of the treatise is divided, Wolff discusses the notion of being in general and the properties that follow from it. In the second part, he is concerned with the various species of being. The first part is divided in turn into three subsections, dealing respectively with the principles of ontology, the essence and existence of being, and the general attributes of being. After Wolff discusses identity and similarity in Chapter 1, he then deals with singular and universal being in Chapter 2. Thus, the discussion of singularity, which for Wolff is equivalent to individuality, precedes the discussion of necessity, contingency, quantity, quality, relation, truth, perfections, and related notions.(12) It is also worthy of note that in the chapter devoted to individuality and universality, individuality is listed and discussed first.

The relative position that individuality occupies in relation to other fundamental metaphysical notions, including universality, indicates the importance that Wolff attached to it as well as its more fundamental and central role in the Ontology. Not that such importance and central role were something new. Throughout the Middle Ages there had been a progressive shift of emphasis from universality to individuality, which is clearly evident as early as the thirteenth century when Duns Scotus discussed universals in the context of individuals in the Opus oxoniense, contrary to what had been customary before him. This shift is most evident in Suárez's Disputationes metaphysicae, where individuality is given separate, prior, and more extensive treatment than all the other common properties of being.

What is most significant and different structurally speaking about Wolff's Ontology, vis-à-vis the later Scholastic tradition, is something else, namely, the epistemic and methodological considerations that are contained in the beginning of the work. They are found in two places. In the Preface Wolff presents some general statements about his modus operandi, indicating among other things that his aim is to make clear notions that are only confusedly found in common as well as in previous philosophical discourse, and also pointing out that he intends to follow the rigorous mathematical method popular among other modern philosophers. In Section 1, he begins the discussion with an examination of the methodological principles that guide his investigation. The principles in question are the "principle of contradiction" and the "principle of sufficient reason." The methodological concerns expressed both in the Preface and in Section 1 are certainly an indication of the epistemic bent that Wolff gave to the Ontology and that do not seem to have affected the work of many late Scholastics. Suárez's Disputationes, for example, go directly from a discussion on the nature of metaphysics to the discussion of the common properties of being and do not contain in the Preface the kind of procedural comments that characterize the Ontology. What distinguishes Wolff's Ontology, then, is that between the discussion of the nature of metaphysics and of the common properties of being he adds a section on methodological principles and that he prefaces the whole work with a series of remarks on the same topic.

Thus, although the Ontology aims to be a work of metaphysics, from its very beginning we are confronted with epistemic and methodological considerations. Does this mean that its contents suffered from the epistemologism that characterize most other modern metaphysical works? I argue yes at least as far as individuation is concerned."

From: Jorge J. E. Gracia - Christian Wolff on Individuation - in: Kenneth F. Barber and Jorge J. E. Gracia (eds.) - Individuation and Identity in early modern philosophy. Descartes to Kant - Albany, State University of New York Press, 1994 pp. 219-243.

(10) Etienne Gilson has discussed at length the implications that Clauvergius's definition of metaphysics and change of terminology had for the discipline in Being and Some Philosophers (Toronto: Pontifical Institute of Mediaeval Studies, 1952), pp. 112ff.

(11) Ontologia, par. 1, p. 1: " Ontologia seu Philosophia prima est scientia entis in genere, seu quatenus ens est." The emphasis in all Latin texts is that of Wolff.

(12) Not all authors use the terms 'singularity' and 'individuality' interchangeably. As far back as the early Middle Ages, Gilbert of Poitiers and others introduced distinctions in their meaning. See my Introduction to the Problem of Individuation in the early Meddle Ages, Munich, Philosophia Verlag, 1986, Chapter 3.


Christian Wolff - Philosophia prima sive Ontologia (1730)


"The Preliminary Discourse on Philosophy in General presents Wolff's master plan for the synthesis of knowledge. Written in 1728, it was intended to serve as the general introduction to his Latin survey of the branches of systematic philosophy, with subsequent volumes on logic, cosmology, empirical psychology, rational psychology, ontology, natural theology, and moral philosophy. Though in writing the Preliminary Discourse Wolff used many notions he intended to develop more fully in these later volumes, the book nevertheless is a basically self-contained discussion; in fact, this work contains Wolff's clearest presentation of his theory of the division and method of the sciences, and its main historical interest lies along these lines.

The overall outline of Wolff's theory is presented in Chapter One of the Preliminary Discourse. He defines history as knowledge of the facts pertaining to both the material world and the world of consciousness, and as such, history provides the empirical foundation of the sciences. But as Aristotle had pointed out centuries earlier, knowledge of the facts is one thing and knowledge of the reason of the facts is quite another thing. This latter constitutes the proper province of philosophy. His third major division of natural knowledge, namely, mathematics, which deals with our knowledge of the quantity of things, employs a method of extraordinary power which is applicable to philosophy; insofar as philosophy shares in the values of mathematical method, it attains to complete certitude. Thus Wolff recognizes the importance of both the empirical methods of historical knowledge and the rational methods of the mathematical sciences. And for him, philosophy is the common meeting ground of these two methods.

The definition of philosophy presented in Chapter Two is of considerable interest. As the science of the possibles insofar as they can be, philosophy must concern itself both with the intelligibility of the world of the possibles and also with the reasons why certain of these possibles become actual. The former is governed by the Principle of Contradiction while the latter is controlled by the Principle of Sufficient Reason. What this means in brief is that for something to be possible it must be internally consistent. The criterion for determining this mutual consistency and intelligibility of the component elements of a possible is the Principle of Contradiction. However, this principle alone does not explain the fact that some possibles are actual while others are not; the mere internal consistency of a possible does not confer actuality upon it. A full understanding of the actual must go beyond the Principle of Contradiction to include an explanation of why this possible rather than another is actual. This further explanation is what is demanded by the Principle of Sufficient Reason. Furthermore, existence is understood by Wolff to be the final complement in the order of possibility." As a result, all philosophical problems for Wolff deal with the constitution and ordering of possibilities or essences. The two great principles are adequate to govern all of these essentialistic relationships, and the door is thus opened for the casting of the entire philosophical enterprise into the formal, deductive pattern outlined in Chapter Four.

Both the order of demonstration within each individual science and the proper subordination of the various sciences to each other are determined by the demands of one continuous deductive sequence. Wolff explains these relationships in great detail in Chapters Three and Four. The individual parts of philosophy are distinguished exclusively on the basis of subject matter or material object divisions, as is clear from the summary on the following page, and each branch of philosophy is carefully located in its proper place of subordination to the more basic disciplines. Further, according to Wolff, the methods of deductive logic apply universally to all these disciplines."

From: Richard J. Blackwell - Introduction to: Christian Wolff - Preliminary discourse on philosophy in general - Indianapolis, Bobbs-Merrill, 1963, pp. IX-XI.

Christian Wolff Classification of sciences

Christian Wolff's Classification of Sciences in the Preliminary Discourse to Philosophy in General (1728)


Wolff's explicit presentation of the Principle of Sufficient Reason occurs at the beginning of his Ontologia. (44) His approach to this Principle and the Principle of Contradiction is not by way of the notion of being and a deduction therefrom, although a cursory glance at the arrangement of his text might lead one to think so, especially after familiarity with later manuals which follow this development. Rather, Wolff makes these "twin pillars of philosophy” more intuitional than deductive; they are the given of the rationalistic mind generating its own data and starting points.(45)

Systematically, the Principle of Sufficient Reason is preceded by the Principle of Contradiction, and Wolff places the foundation of this latter in an obvious experience of mental life: While we are judging something to be, it is impossible at the same time to judge it not to be(46) From this conscious experience of the nature of our minds, we concede without need of proof the proposition enunciated in general terms as the Principle of Contradiction: It cannot happen that one and the same thing be and at the same time not be. Or, another form of the same: If A is B, it is false that the same A is not B.(47)

To demonstrate the fecundity of this basic axiom, Wolff explores its logical implications and leaves little doubt that the principle for him is a purely formal one, a kind of aliquid to which subsequent concepts in his system may be tied. If it were not a true principle, he argues, then the same predicate could and could not pertain to the same subject under the same determinations, and the same proposition could be both false and true at the same time.(48) Besides "contradiction is simultaneity in affirming and denying,"(49) it is contained in two propositions, of which "one takes away what the other posits."

The important point is that the process of building concepts and working out demonstrations is insured by this principle against logical failure. Negatively, it is important to note that while this treatment is placed under ontology and the subject of being in general, yet with no systematic reference to or involvement of existential judgment or sensation, it is not possible to denote this principle as anything more than logical.

Proceeding next to the Principle of Sufficient Reason, Wolff does not make any detailed reference to the question of its relation to the Principle of Contradiction. To anyone following through within the system itself, the question of whether it reduces to the Principle of Contradiction is answered by the fact that the latter is the one systematically prior, and this priority makes reduction possible.(50)

Clearly, the dual sovereignty granted these principles by Leibniz no longer holds. Leibniz had located the relation between the Principle of Contradiction and the Principle of Sufficient Reason in the realm of the rational through his distinction between necessary and contingent truths. Wolff unified that realm of the rational around the Principle of Contradiction.(51) Again we can note the lack of existential reference in the fact that this realm remained distinct from that of the singular concrete sensible data of experience. Under the influence of Locke and the rise of empirical science, Wolff and his successors heightened the reality of this latter realm and deepened the realization and the value of its experience. But the systematic failure to incorporate it into an existential union with the realm of the rational will continue to haunt modern philosophy.

Unity in the order of essence, however, is impressively systematic. The possible as the non-contradictory, we shall see, gives to the Principle of Contradiction a primacy which it can share with no other. The ratio or reason whereby things are understood is ultimately explicable in terms of the opposition between "nothing" and "something," the latter being the systematic coherence of clear and distinct ideas whose right to, and precise determination of, a place in the system ultimately depends on the Principle of Contradiction. The Non-Contradictory is "something."(52)

This application of the primacy of essence to a theory of method grants priority to the Principle of Contradiction over the Principle of Sufficient Reason, and to the Principle of Sufficient Reason over causality. In other words, when Wolff has defined philosophy in terms of possibles rather than causes, he must use ratio instead of causa to describe the object of the metaphysical search, and it is one of the inevitabilities of such a system that "reasons grow more rational and logical; causes, more empirical and real."(53) The deductive method of mathematics becomes the unique method of philosophy, and here-and-now existential reference is obtained by "common sense" joined sometimes with a pious use of Sacred Scripture.

By "Sufficient Reason," Wolff meant whatever explains why something is; it is "that whence it is understood why anything is."(54) He gives two examples: The three sides of the triangle, or rather, its three-sidedness is sufficient reason for the three angles because this suffices for us to understand the triangle as having three angles.(55) In the order of motivation and action he further instances the case of a man rising to his feet out of respect for some person who has just entered the room. From the fact of this entry, plus the reverence due the newcomer, it can be understood why the man in the room rises to his feet and hence a sufficient reason for the action is assigned.

In keeping with his methodology of building notions and demonstrations from previously established concepts, it is now necessary to define the meaning of "nothing" and "something" as involved in the notion of "sufficient reason." This is very simply managed in terms of the basic building block itself, the notion or concept. We call that "nothing" to which no notion corresponds. And "something" is that to which some notion can be attributed or corresponds.(56)" pp. 35-38.

From: John Edwin Gurr - The principle of sufficient reason in some Scholastic systems 1750-1900. Milwaukee, Marquette University Press, 1959.

(44) Wolff, Philosophia prima, No. 70 ff.

(45) Part I of the Ontologia bears the title, "Concerning Being in General and the Properties Which Flow Therefrom." But this first part immediately divides into two parts: Section 1, "Concerning the Principles of First Philosophy," and Section II, "Concerning Essence and Existence and certain related notions of being." Section I is composed of two chapters devoted to the two Principles, Contradiction and Sufficient Reason. It is only in Section II that he takes up the discussion of being and its notions, a discussion which proceeds by way of the possible and impossible, determined and indetermined, to Chapter III, "Concerning the Notion of Being."

It is within this framework as taken over by the successors of Wolff that we see the Principle of Sufficient Reason migrate back and forth as to relative position in the subject matter. In Bü1lfinger ( Dilucidationes), for instance, the Principles come after the treatment of the possible-impossible, necessary and contingent. In John G. Feder's lnstitutiones logicae et metaphysicae (Editio quarta; Gottingen: J. Dietrich, 1797 preface 1777), No. 63, they appear in the Logic, part II, "Concerning the right use of the intellect in seeking truth," Chapter I, "Concerning the principles of truth and the various modes of knowing them." To this migratory characteristic of the Principle of Sufficient Reason we shall return in Chapter Six.

(46) Wolff, Philosophia prima, sive ontologia, No. 27. So also with the Principle of Sufficient Reason, as we shall see below.

(47) "Naturae igitur mentis nostrae nobis conscii ad exempla attendentes sine probatione concedimus propositionem terminis generalibus enunciatem: Fieri non potest, ut idem simul sit & non sit, seu quod perinde est, si A sit B, falsum est idem A non esse B, sive A denotet ens absolute consideratum, sive sub data conditione spectatum." Ibid., No. 28. "Propositio haec: Fieri non potest, ut idem simul sit & non sit, dicitur Principium Contradictionis, ob rationem mox adducendam. Principium autem Contradictionis jam olim adhibuit Aristoteles eodem usi sunt Scholastici in philosophia prima instar axiomatis generalis." Ibid., No. 29.

(48) Ibid., Nos. 30, 31.

(49) Ibid., No. 30.

(50) Wilbur Urban, "The History of the Principle of Sufficient Reason: Its Metaphysical and Logical Formulations," Princeton Contributions to Philosophy, I, No. 3 April, 1900, p. 27. Urban sees in paragraphs Nos. 66-70 a statement of the Principle of Sufficient Reason as a logical law by means of deduction from the law of contradiction; he finds Wolff, in confusing real grounds with the grounds of knowledge, guilty of a petitio principii. Hans Pichler, Über Christian Wolff's Ontologie (Leipzig, Durr'schen Buchhandlung, 1910), p. 7, calls Wolff's proof a word-play.

(51) Émile Bréhier, Histoire de la philosophie (Paris: Alcan, 1934), Vol. II, part II, 361.

(52) Wolff, Philosophia prima, Nos. 59-59.

(53) Norman Wilde, Friedrich Henrich Jacobi: A Study in the Origin of German Realism (New York: Columbia College, 1894), p. 27.

(54) Wolff, Philosophia prima, No. 56.

(55) The triangle example is reminiscent of Spinoza, and a favorite example with rationalists. Like Leibniz, Wolff was still faced with the threat of Spinozism. With no systematic distinction between the true and the real that is supported by existential reference, his only escape from being pushed into Spinoza's universe-version of "everything that exists has a cause or reason why it exists" was to assert as a starting point the reality of the possible. The primacy of essence has a way of becoming the primacy of the logically necessary, where what is not impossible is necessary, i.e., is.

(56) “Nihilum dicimus, cui nulla respondet notio.” Wolff, Philosophia prima, No. 57; cf. Nos. 59 and 60.


"Because the being of Wolff's metaphysics is possible being, existence is not one of its essential determinants. In fact, Wolff defines existence as ". . . The complement of possibility. And existence is also called Actuality. " (44) Because existence is neither an essential of being nor an attribute inseparable from it, existence must be regarded as a mode. Hence it will depend upon a cause outside the being which possesses it. Therefore, as Gilson observes, in the philosophy of Christian Wolff, "the sufficient reason for the actual existence of any finite being is never to be found in that being itself; it always is to be found in another one." (45)

All this is necessary for a proper understanding of Wolff's definition of substance as a subject which is modifiable and perdurable. Because substance in Wolff's ontology is a possible being, it can be readily seen why Wolff calls it a subject which is modifiable rather than modified. The being of Wolff's metaphysics is possible being, not actual or existent being. Modes are characteristics or determinations of existent being, consequently while a substance is conceived as capable of having modes (capax aliorum), these accidental determinations are never actually possessed by it in its ontological or possible existence."

From John V. Burns - Dynamism in the cosmology of Christian Wolff. A study in pre-critical rationalism - New York, Exposition Press, pp. 28-29

(44) Ibid., No. 174.

(45) Gilson, Being and Some Philosophers, p. 119.

"And this is why, in the philosophy of Christian Wolff, existence is completely excluded from the field of ontology. There are special sciences to deal with all the problems related to existence and none of them is ontology. Are we interested in finding out the sufficient reason for the existence of God or for that of the world? Natural theology will give the answer. Do we want to know how those beings which make up the material world are, though contingent, yet determined? Cosmology will inform us about it. Are we wondering how, in the human mind, the possibles are drawn from potency to act? Psychology holds the key to that problem. When today we make use of the term, 'ontology,' what it means to us is just the same as 'metaphysics.' Not so in the philosophy of Wolff, who needed a new word to designate a new thing. Strictly speaking, an ontology is a metaphysics without natural theology, because it is a metaphysics without existence." Ibid.