The question "how are logic and ontology interrelated?" is an ambiguous question, that is, it can refer either to logic and ontology
themselves or to the metatheories of logic and ontology (that is, to the views about them). Furthermore, in the first case, both logic and ontology may be
considered either objectively or subjectively.
(1) If the question refers to logic and ontology themselves considered objectively (that is, in their content), the disciplines are seen as
sets of laws and/or rules, and so the problem is purely logical. It will be clear that its solution depends largely on the content of logic and of ontology as
they were constructed at a given time.
(2) If the question refers to the same, but as seen subjectively (that is, in as far as they were conceived by some thinkers or groups of
thinkers), then it is about empirical facts and is then a historical question: how did the fact that x held the ontology O influence the fact that he
also held the logic L or inversely?
(3) Finally, if the question is concerned not with the two systems as they are but rather with the metatheoretical views about them (that is,
with the corresponding philosophies of logic), the question is a quite different one. That this is so is indicated by the fact that often the same type of
logic was philosophically interpreted in a different manner by two different schools. This question, in turn, can be considered either logically or
historically. It should be clear that the first question is fundamental. Therefore, the principal focus of this presentation will be upon it. The philosophy of
logic and ontology will be treated only secondarily, while the historical question of the mutual factual influences of doctrines about them will be only
Now to state at once one of the principal conclusions of the present investigation, it must be confessed that there is considerable confusion
about that basic question. Almost any imaginable answer has been proposed by one or another philosopher. To mention only two of the extreme views, respectable
logicians have maintained that there is a complete identity of both disciplines (thus, Scholz) and that there is no relation whatsoever between them (thus,
Nagel). The very fact that this is so requires an explanation. As is always so in such cases, this explanation must be historical.
One reason for the unfortunate state prevailing in investigations of this problem can readily be identified: ignorance. Most ontologists do
not know even the ABC's of logic. But the inverse is also true: most logicians do not have the least idea what ontology might be. These deficiencies are often
combined, on both sides, with value judgments of an unkind sort. Thus, to most ontologists, logic does not seem to be a serious discipline, although they
concede that it provides (hélas!) some practical results for computer science. On the other hand, ontology is merely nonsense in the estimation of many
logicians. It is little wonder that such scholars produce few worthwhile contributions regarding the relations of the two disciplines.
But this is not the whole answer. The present bifurcation did not always prevail. There have been ontologists who were well instructed in
logic and who were even creative logicians in their own right ; Thomas Aquinas and Uddyotakâra (seventh century) are examples. There were also logicians who
knew a good deal about ontology; one need think only of Leibniz and of Whitehead. Nevertheless, confusion about our problem is widespread across the ages. Some
explanation must be offered for this fact, and once again it has to explained historically. (pp. 274-275)
The history begins with Aristotle, as so many philosophical questions do. Nor is it a question of that history merely beginning with him. For
in many cases one gets the impression that where "the Master of those who know" (Dante) failed to perceive or to formulate a problem, his successors had a
difficult time at formulating or solving it. Among these problems is that of the relations between logic and ontology.
The following is a brief description of both disciplines as they appear to the unbiased reader in the Aristotelian corpus. There is a book,
or rather a collection of writings, called "Metaphysics" by Andronikos Rhodes. There is also a collection of works which received the name
"Organon" from the commentators. None of these names derive from Aristotle himself. There can be no doubt, however, that we find in his writings a
considerable number of doctrines belonging to what will subsequently be called 'logic" and "ontology" respectively.
As regards ontology, Aristotle talks about a "first philosophy" and a "divine science." He says that they are about being as being; what we
see here is an attempt to define this discipline. But as far as logic is concerned, we find no name for it in his writings. (...) Still less is there any
attempt to define the subject matter of logic.
If, however, we turn from his philosophy of logic and of ontology to the theories themselves (that is, to the systems Aristotle developed),
it is relatively easy to describe what he would have meant by "ontology" and "logic" respectively, if he had such terms.
Regarding ontology, we should first note that Aristotle, unlike many later thinkers, did not believe that there is an entity or even a
meaning unambiguously associated with the term "being." In one of those passages which can certainly be esteemed as a stroke of genius, Aristotle explicitly
states that "being" is an ambiguous term; he justifies this assertion by a sort of embryonic theory of types. And yet, we find extensive discussions of the
characteristics of entities in general in the Metaphysics and elsewhere. On closer inspection, we discover that his ontological doctrines can be
divided into two classes.
First of all, in the fourth book of his Metaphysics, Aristotle undertakes to state and discuss the "principles" -- namely, non-contradiction
and the excluded middle. (Aristotle made explicit use of the principle of identity in his logic, but never made it the object of a similar study.) Next we have
a number of analyses of concrete entities. Of these the most conspicuous are the doctrine of act and potency and the table of the categories (also studied in
the Organon, but obviously belonging to the "first philosophy"). The last named could be and has often been viewed as a classification of entities.
But it seems more consistent with Aristotle's thought to consider it as a sort of analysis of a concrete entity into its various aspects. (...)
In summary, the Aristotelian ontology appears to be a study (1) of (isomorphically, we would say) common properties of all entities and (2)
of the aspects into which they can be analyzed. Both sorts of studies are about real objects. One distinctive characteristic of this ontology is its
conspicuous lack of existential statements, which is contrary to what we find in what is now commonly called "metaphysics". (pp. 279-281)
In summary, then, Aristotle left: (1) an ontology conceived as a theory of real entities in general and of their most general aspects; this
discipline is defined; (2) two quite different systems of logic: a technology of discussion and an object-linguistic formal logic; (3) a considerable
overlapping of both disciplines (for example, the "principles," the categories, etc.) ; (4) not even a hint, direct or indirect, as to what formal logic might
be about ; in other words, no philosophy of logic at all.
It should be clear that in that frame of reference, the question of the relations between logic and ontology cannot even be clearly stated.
For we do not know what logic is nor which of the two logics has to be considered nor where are the boundaries between it and ontology.
And yet that is the frame of reference within which most of the Western discussions of our problem will develop. That is, so it seems, the
explanation of the confusion reigning in our field.
With the Stoics, we find a clear choice between the alternative conceptions of logic: they opt for
"dialectics," the art of arguing. This does not mean that they remained at the level of the Topics. On the contrary, their logic of propositions, magnificently
developed, is formal logic. But it is conceived as being a set of rules of arguing.
Moreover, the Stoics were the first to formulate a consistent theory of the object of logic. Logic is, according to them, radically different
from ontology of the Aristotelian type. There is, it is true, no ontology in their philosophy; and what corresponds to the Aristotelian table of categories is
considered to be a part of logic. But the subject matter of logic, the meanings, is sharply distinguished from what is real. For, whereas everything which is
real, including mental entities, is a body in the Stoics' view, the meanings are not bodies. They are ideal entities.
Thus the first known philosophy of logic emphasizes the radical difference and independence of logic as regards ontology.
The Scholastics make no use of the term "ontology" and discuss subjects which will subsequently be called
"ontological" in the context of their commentaries on Aristotle's Metaphysics. As compared with the latter, there are some important developments. For example,
much consideration is given to the semantic status of "being." We are aware of several positions adopted regarding this problem: while the Thomists considered
"being" as analogous (that is, basically a systematically ambiguous term), others, such as the Ockhamists, held that it was purely ambiguous; Scotists, on the
other hand, claimed that it is a "genus" (that is, not an ambiguous expression). Depending on the position assumed, some philosophers will develop a general
theory of being, while others will not. In addition, we find a few new chapters in ontology: above all, the doctrine of the distinction between essence and
existence, the theory of the "transcendental" properties of all entities, and, of course, a rich technical elaboration of every doctrine. With these
exceptions, the subject matter of ontology is the same as that found in Aristotle.
When we turn to logic, the situation is quite different. While incorporating and developing a number of Aristotelian doctrines, Scholastic
logic is very much un-Aristotelian insofar as its method and approach are concerned, but also, to a large extent, as regards the content. It is completely
metalinguistic and consists of rules. But it is unlike Stoic logic as well, for its explicit concern is not with mere meanings but rather with what were called
propositions (meaningful sentences). Semantics undergoes tremendous development during this period.
This being so, several important facts which are relevant to our problem emerge. First of all, a sharp distinction between logic and ontology
is explicitly established: the former is metalinguistic, the latter, object-linguistic; logic formulates rules, ontology, laws. Secondly, given this
distinction and the nature of the Aristotelian corpus, a curious duplication of doctrines appears: problems are treated twice, once in logic and then again in
ontology. As Ockham noted, there are two principles of noncontradiction: one ontological, stated in object-language, and another logical, formulated in meta-
The Scholastics also formulated various philosophies of logic. They had several common views. For one, logic, while being primarily a
methodology of reasoning and arguing, is said to be also a theory of certain entities. Second, they all shared the assumption that logic is not about "first
intentions," which are dealt with in ontology, but rather about "second intentions." However, these terms assumed very different meanings in the context of
different schools. (pp. 282-283)
The modern era, prior to the rise of mathematical logic, is an alogical and a largely unontological period.
It opens with the Humanists; in their view, if logic has any usefulness at all, it is only as a set of rules for everyday arguments: it is an inferior sort of
rhetoric, as Valla put it. Later on, when the scientific spirit began to rise, even the most rationalistic thinkers, such as Descartes, would not dare to
reconsider the Humanists' total condemnation of "scholastic subtleties," including formal logic. Gradually, the so-called conventional logic was
The latter consists of extracts from Scholastic logic which omit almost every logical matter not connected with the theory of the assertoric
syllogism (thus, the logic of propositions among others) and with the addition of a number of methodological doctrines. Logic is quite clearly conceived of as
"dialectics," "the art of thinking," as the authors of the influential Logique de Port-Royal titled it. Philosophically, there is a novelty:
widespread psychologism, according to which logic has as its object mental entities and activities (concepts, judgments, reasonings).
There is, of course, one great exception -- Leibniz, a logician of genius and an important
thinker in the field of ontology. His ontology has been popularized by Wolff; in the latter's work the term "ontology" is clearly defined as designating the
most general part of metaphysics, dealing with "being in general" (quite in the Aristotelian spirit). Leibnizian logic is mathematical and should rather be
considered together with more recent logics, for its influence on the seventeenth, eighteenth, and nineteenth centuries was almost negligible. Leibniz also
established his own philosophy of logic, which can only be understood in light of his logic. Our discussion of this will be deferred as well.
But, apart from Leibniz, the situation of our problem is not much different from that found in the Stoics and Scholastics: as logic is
concerned with the mental behavior of men and ontology with being in general, the separation of the two is just as sharp as in the older schools. Indeed, this
separation is reinforced by the fact that logic is now thought of as being a purely practical discipline and not as a theoretical one.
The whole course of the evolution between Aristotle and Boole may be summarized as follows. Ontology, whenever present, is on the whole of
the Aristotelian type: a general theory of real entities. Regarding logic, the great majority of thinkers opt for the first Aristotelian logic, that of the
Topics; they cultivate this discipline as a methodology of thought. While it is true that some Scholastics admitted a theory founding such a methodology, their
logic nevertheless belongs to the type outlined in the Topics, not to that of the Prior Analytics. With such an assumption as a basis, whatever philosophy of
logic they developed--whether conceived as a theory of meanings, of second intentions, of syntax or of mental entities, it was always radically different from
ontology." (pp. 284-285)
From: Joseph Bochenski, "Logic and Ontology", Philosophy East and West, 24, 1974, pp. 275-292.
"Aristotle was the founder not only of logic in western philosophy, but of ontology as well, which he described in his Metaphysics
and the Categories as a study of the common properties of all entities, and of the categorial aspects into which they can be analyzed. The principal
method of ontology has been one or another form of categorial analysis, depending on whether the analysis was directed upon the structure of reality, as in
Aristotle's case, or upon the structure of thought and reason, as, e.g., in Kant's Critique of Pure Reason. Viewed in this way, the two subjects of
logic and ontology could hardly be more different, and many schools in the history of philosophy, such as the Stoics, saw no common ground between them. Logic
was only a system of rules for how to argue successfully, and ontology, as a categorial analysis and general theory of what there is (in the physical
universe), was a system of categories and laws about being.
Scholastic logicians also drew a sharp distinction between logic and ontology, taking the latter to be about ‘first intentions’ (concepts
abstracted directly from physical reality), and the former about ‘second intentions’ (concepts abstracted wholly from the ‘material’ content of first
intentions, as well as about such categorial concepts as individual, proposition, universal, genus, species, property, etc., and so-called syncategorematic
concepts such as negation). According to Aquinas, second intentions have a foundation in real entities, but 'exist' only in knowledge; i.e., they do not exist
in the real world but depend on the mind for their existence – which is not say that they are subjective mental entities." (p. 117)
From: Nino Cocchiarella, "Logic and Ontology", Axiomathes vol. 12, 2001, pp.
"Ancient and medieval history of ancient logic.
One meets sometimes with the assertion that history of philosophy is an invention of the XVIIIth century. This is in so far correct, that in
older times -- in spite of Aristotle's and Thomas Aquinas' explicit teaching -- scholars neglected completely the genetic point of view in history of logic; on
the other hand, thorn is no doubt that another aspect of historiography, namely the understanding of doctrines, was much cultivated by ancient and medieval
thinkers. A complete account of ancient logic would have to take their results into consideration. Unfortunately, we know practically nothing of all the huge
work which was accomplished, especially on Aristotle, by Greek, Syrian, Arabian, Jewish, or, above all, by Latin medieval logicians: as was already stated, the
Greek commentators have not yet been studied, while the others are little more than a field for future research. And yet, we know that there were important
discoveries during that time. This has been proved at least in one particularly striking instance: Albertus Magnus had a perfect understanding (superior to
that of Alexander [of Aphrodisias], not to mention Prantl) of the highly difficult Aristotelian modal logic. This understanding has been nearly completely
lost, however, during the modern ages.
State of the history of formal logic during the XIXth century.
Modern history of Logic had been started during the XIXth century, but its state was very bad at that time -- indeed until 1930 approximately
-- because of two phenomena. On one hand, most of the historians of logic took for granted what Kant said on it; namely that "formal logic was not able to
advance a single step (since Aristotle) and is thus to all appearance a closed and complete body of doctrine" (*); consequently, there was, according to them,
no history of logic at all, or at the most, a history of the decay of Aristotelian doctrines. On the other hand, authors writing during that period were not
formal logicians and by "logic" they mostly understood methodology, epistemology and ontology. That is why e.g. Robert Adamson could devote 10 pages to such a
"logician" as Kant -- but only five to the whole period from the death of Aristotle to Bacon, i.e. to Theophrastus, the Stoic-Megaric School and the
Scholastics. In order to realize what this means, it will be enough to remember that from the point of view we assume here, Kant is not a logician at all,
while the leading Megaricians and Stoics are among the greatest thinkers in Logic.
The worst mischief was done during that period by the work of Carl Prantl (1855). This is based on an extensive knowledge of sources and
constitutes the only all-embracing History of Ancient Logic we have until now. Unfortunately, Prantl suffered most acutely from the two above-mentioned
phenomena: he believed firmly in the verdict of Kant and had little understanding of formal logic. Moreover, he had the curious moralizing attitude in history
of logic, and, as he disliked both the Stoics and the Scholastics, he joined to incredible misinterpretations of their doctrines, injurious words, treating
them as complete fools and morally bad men precisely because of logical doctrines which we believe to be very interesting and original. It is now known that
his work -- excepting as a collection of texts (and even this far from being complete) -- is valueless. But it exercised a great influence on practically all
writers on our subject until J. Łukasiewicz and H. Scholz drew attention to the enormous number of errors it contains.
We may place the beginning of recent research in our domain in 1896 when Peirce made the discovery that the Megaricians had the truth-value
definition of implication. The first important studies belonging to the new period are those of G. Vailati on a theorem of Plato and Euclid (1904), A. Rüstow
on the Liar (1908) and J. Łukasiewicz (1927); the Polish logician proposed in it his re-discovery of the logical structure of the Aristotelian syllogism and of
Stoic arguments. Four years later appeared the highly suggestive, indeed revolutionary, History of Logic by H. Scholz, followed in 1935 by the paper
of Łukasiewicz on history of logic of propositions; this is considered until now as the most important recent contribution to our subject. Both scholars --
Łukasiewicz and Scholz -- formed small schools. J. Salamucha, the pupil of the former, wrote on Aristotle's theory of deduction (1930) and the present author
on the logic of Theophrastus (1939). Fr. J. W. Stakelum, who studied with the latter, wrote a book on Galen and the logic of propositions. On the other hand,
A. Becker, a student of H. Scholz, published an important book on Aristotle's contingent syllogisms (1933). Professor K. Dürr was also influenced by
Łukasiewicz in his study on Boethius (1938); his results were somewhat improved by R. van den Driessche (1949). In the English speaking world we may mention
the paper of Miss Martha Hurst on implication during the IVth century (1935) -- but above all the already quoted work of Dr. B. Mates on Stoic Logic (in the
press [published 1953]), which, being inspired by Łukasiewicz and his school may be considered as one of the best achievements of recent research.
Such is, in outline, the work done by logicians. On the other hand philologists had considerable merits in the study of ancient logic. We
cannot quote here all their contributions, but at least the important book of Fr. Solmsen (1929) on the evolution of Aristotle's logic and rhetoric must be
mentioned, and, above all, the masterly commentary on the Analytics by Sir W. D. Ross (1949). It does not always give full satisfaction to a logician trained
on modern methods, but it is, nevertheless, a scholarly work of a philologist who made a considerable effort to grasp the results of logicians." (pp. 4-7, some
(*) Kritik der reinen Vernunft. 2d ed. p, VIII (English by N. Kemp Smith)
References (edited by R. Corazzon)
Robert Adamson, A short History of Logic, edited by W. R. Sorley, London 1911.
Albrecht Becker, Die Aristotelische Theorie der Moglichkeitsschlusse. Eine logisch-philologische Untersuchung der Kapitel 13-22 von
Aristoteles' Analytica priora I (Dissertation, University of Munster), Berlin 1933.
Józef M. Bochenski, "La logique de Théophraste", Collectanea logica, 1, 1939, pp. 195-304) second edition Fribourg: Librairie
del'université 1947 (reprint New York: Garland 1987)
René van den Driessche, "Sur le "De Syllogismo Hypothetico" de Boece", Methodos, 1, 1949, pp. 293-307.
Karl Dürr, "Aussagenlogik im Mittelalter", Erkenntnis 7, 1938, pp. 160-168.
Martha Hurst, "Implication in the 4th Century B.C.", Mind 44, 1935, pp. 484-495.
Jan Łukasiewicz, "O logice Stoików" (On the Logic of the Stoics), Przeglad Filozoficzny 30, 1927, pp. 278-279.
Jan Łukasiewicz, "Zur Geschichte der Aussagenlogik" (On the history of the logic of propositions), Erkenntnis, 5, 1935, pp. 111-131
(English translation: Storrs McCall (ed.), Polish Logic 1920-1939, Oxford: Clarendon Press 1967, pp. 66-87 and L. Borkowski (ed.), Jan
Łukasiewicz. Selected Works, Amsterdam: North-Holland 1970, pp. 197-217.
Benson Mates, Stoic Logic Berkeley: University of California Press 1953 (second edition 1961).
Charles Sanders Peirce, "The regenerated logic", The Monist, 7, 1896, pp. 19-40.
Carl Prantl, Geachichte der Logik im Abendlande (Manuldruck) 2 vols., Leipzig 1927.
David W. Ross, Aristotle's Prior and Posterior Analytics... with Introduction and Commentary, Oxford 1949.
Alexander Rüstow, Der Lügner. Theorie, Geschichte und Auflösung des Russellschen Paradoxons, (Dissertation at the University of
Erlangen, 1908), Leipzig 1910.
Jan Salamucha, Pojiecie deduckcji u Aryatotelesa i św. Tomasza z Akwinu (The Concept of Deduction in Aristotle and St. Thomas
Aquinas). Warezawa 1930 (See the review by Józef M. Bochenski (1935), translated in: Kordula Świętorzecka, Jacek Juliusz Jadacki (eds.), Jan Salamucha.
Knowledge and Faith, Amsterdam: Rodopi, pp. 311-316).
Heinrich Scholz, Geachichte der Logik., Berlin 1931 (English translation: A Concise History of Logic, New York, 1961.)
Friedrich Solmsen, Die Entwicklung der Aristotelischen Logik und Rhetorik, Berlin 1939.
James W. Stakelum, Galen and the Logic of Propositions (Dissertation, Rome, Angelicum), Romae 1940.
Giovanni Vailati, "A proposito d'un passo del Teeteto e di una dimostrazione di Euclide", Rivista di Filosofia e di scienze affini,
6, 1904, pp. 378-388.
From: Joseph Bochenski, Ancient Logic, Amsterdam: North-Holland 1951.