A plea for epistemic ontologies

1. Introduction

The ontologies developed in the discipline of Applied Ontology are catalogs of categories or classes of objects provided with being. These catalogs are structured by means of different relations (e.g., subsumption, parthood, and dependency). A common and strongly encouraged approach to establishing this catalog consists of using theories of philosophical ontology (metaphysics), i.e. inventories of categories considered to be fundamental for classifying all that is, to organize the ontology’s top level as a small set of abstract categories, referred to as a “foundational” ontology.1

For each human being, existence is a common-sense notion rooted in our relationship with our environment. Experience teaches us that inanimate objects and living beings with which we interact come into existence but also cease to exist. In metaphysics, modes of existence are recognized, and one commonly admits a main distinction between concrete and abstract entities: concrete entities are physical entities that enjoy a spatiotemporal existence independent of all human thought,2

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Fig. 1.

A foundational ontology, taken from (Rosenkrantz and Hoffman, 1991, p. 839).

In metaphysics, and taking the example of the foundational ontology developed by Rosenkrantz and Hoffman (1991) (Fig. 1), the distinction between concrete and abstract entities commonly acts as the first structuring principle for an ontology. Nonetheless, Rosenkrantz & Hoffman consider that this distinction (albeit very useful) does not rest on well-established, indisputable metaphysical bases (ibid., fn 9):

The distinction between concrete entities and abstract entities that we are employing is an intuitive one. The intuitive distinction may be difficult to analyze, but it is serviceable nonetheless. The distinction in question seems indispensable in ontology and is presupposed by realists and antirealists in their debates about the problem of universals.

R&H emphasize that along with an intuitive partition of the world between concrete and abstract entities comes the “problem of universals” concerning the recognition (or the denial) of existence of generic entities that allow us to explain resemblances between individual entities. We will have the opportunity to address this issue.

In Applied Ontology, the situation is different: one can identify several strategies. While GFO recognizes four first-level domains of entity (physical, mental, social, and ideal) on the basis of distinct modes of existence, a commonly implemented first structuring principle consists in distinguishing between endurants (continuants) and perdurants (occurrents). This is particularly the case for DOLCE (of which Fig. 2 presents an extract of the main categories) and BFO. One such distinction concerns how entities persist over time, which indirectly reflects distinct modes of existence. In short, endurants are three-dimensional entities existing in their full identity at every moment of their existence, while perdurants are four-dimensional entities that derive their existence from gaining parts over time. Returning to the distinction between concretes and abstracts, we note that DOLCE contains an Abstract category subsuming Facts, Sets and Regions, in particular spaces of magnitudes of qualities Space Regions made up of atomic magnitudes Qualia (Quale in the singular). The authors of DOLCE define an abstract entity as being neither spatial nor temporal, which reminds the usual characterization of ideal objects in metaphysics.3

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Fig. 2.

An extract from the DOLCE foundational ontology (Borgo et al., 2022a).

Going beyond the differences in the way the world is partitioned, let us look at the common features of the current foundational ontologies and notably their ontological commitments. Following Borgo et al. (2022b), we can abstract a metaphysical thesis (MT) and a semantic thesis (ST) underlying the definition of these ontologies. We distinguish these theses from the methodological principle (MP) adopted for the design of these artifacts that are ontologies.

(MT) refers to the notion of “domain”. As mentioned above, today’s foundational ontologies partition the world into broad domains but in different ways (i.e. on the basis of different philosophical principles). However, all the ontologies have some common features, such as a claim to commit to “physical realism”: a physical world exists independently of whether we think about it or not. This metaphysical thesis is distinct from the methodological principles that most current ontologies put forward and thus complements (MP).

This is the case for BFO, whose authors defend a principle of “ontological realism”, as recently emphasized by Otte et al. (2022, p. 18):

The goal of an ontology is to describe reality. Scientific investigation is concerned with general features of reality and relations among them. Consequently, BFO consists fundamentally of representation of reality rather than language, concepts, or mental representations about reality.

We interpret this principle as giving priority to physical entities in the development of artifact ontologies. The validity of this principle was the subject of a debate in 2010 between Gary Merrill (2010) on one hand and Smith and Ceusters (2010) on the other. This debate then opened into a metaphysical discussion about the existence of universals, with Merrill championing the nominalism of universals. One of the issues with this type of doctrine is deciding what ontological categories correspond to (i.e. what they represent). Merrill’s nominalism of universals prompted him to opt for categories that correspond to concepts; he therefore advocated the development of conceptualist ontologies. On the other hand, BFO’s authors point out that their categories mainly represent universals (some specific categories, like Medical doctor or Dog or cat, are classes defined on the basis of universals).

Ever since the DOLCE ontology was first developed, its authors (Masolo et al., 2003) have claimed cognitive bias in how reality is apprehended (as recalled by Borgo et al. (2022a, p. 45)):

DOLCE is inspired by cognitive and linguistic considerations and aims to model a commonsense view of reality.

This principle advocates that the criteria for selecting categories should take into account of the way in which language and human conceptions (especially common sense) shape our divisions of reality. This prompted DOLCE’s authors to favor “descriptive” ontologies over “referentialist” ones (Masolo et al., 2003):

We do not commit to a strictly referentialist metaphysics related to the intrinsic nature of the world: rather, the categories we introduce here are thought of as cognitive artifacts ultimately depending on human perception, cultural imprints and social conventions (a sort of « cognitive » metaphysics).

DOLCE is thus an ontology of particulars with a cognitive imprint; that is the meaning we give to the term “descriptive”. It is also worth noting that, unlike BFO, there is no precise metaphysical commitment to the nature of the generic entities represented by the categories, the meaning of the categories being fixed by the formal axiomatics of the ontology.

For their part, the authors of GFO developed the principle of “integrative realism” to underpin their ontology (Burek et al., 2020, pp. 34–35):

GFO postulates the existence of a reality that is independent of the mind. Integrative realism is determined by two features. First the subject has access to real and independent entities of the world only through concepts, being part of the mind. Secondly, there is a law-like correspondence between the subjective phenomena of the mind and the independent reality. This approach leads to a new understanding of the relation between ontology and epistemology, because both cannot be separated. Ontology is directed at the independent objects of the world, though these appear to the subject through the knowledge (involving perception and concepts) that the subject has about them. This leads, we believe, to a new interpretation of works by G. Frege, B. Russell, and K. Twardowski.

In this excerpt, GFO’s authors begin by acknowledging the thesis of physical realism. The principle of “integrative realism” is then stated as two psychological theses: (i) our access to physical reality is only mediated by concepts (here, we note a proximity with the notion of descriptive ontology put forward by DOLCE’s authors, except that, as we already pointed out, the latter is not based on a particular psychological thesis); and (ii) psychic phenomena correspond closely to physical reality (this thesis concerns our knowledge of reality without, however, specifying which part of reality is reflected by our knowledge). In fact, GFO’s authors use these psychological theses as a pretext for re-evaluating the articulation between epistemology and ontology.

In the present article, we shall follow exactly the path suggested by GFO’s authors. It will lead us to define a new class of ontology that we call epistemic – a kind of conceptualist ontology. As we shall see below, an epistemic ontology is an ontology of particulars (like BFO, DOLCE and GFO). It differs from a descriptive ontology in that the particulars in its domain are mental objects of thought; in other words, they are conceptual in nature. Our approach to definition consists in favoring the ontology of the mind and in placing “knowledge objects” in our inventory of the furniture of the world.4

To understand the relationship between the mental and physical domains, we choose to focus on intentionality, that is to say, our ability to think and to refer to extramental entities. This ability has been one of the central questions in philosophy and metaphysics since antiquity and is covered by Aristotle’s treatise of psychology known as De Anima in Latin. For the purposes of this study, we choose to refer to work performed at the turn of the 20th century in the Brentanian school. Franz Brentano is unanimously recognized as the philosopher who reintroduced the concept of intentionality into the contemporary philosophical debate.5

The (MP)’ principle consecrates our notion of an epistemic ontology. These are ontologies whose categories correspond to general objects of thought or knowledge. The notion of an epistemic ontology is based on a metaphysical framework that acknowledges the existence of specific mental objects representing extramental entities, as expressed by the thesis (MT)’. Consideration of (MT)’ prompts one to investigate the frontier between the mental world and the physical world. In the second part of this manuscript, we build on our previous work on the nature of physical processes and events (Kassel, 2019; 2020; 2022) and investigate three domains of entities – technical artifacts (§ 3), material qualities of physical objects (§ 4), and events (§ 5) – which leads us to outline an epistemic foundational ontology.

In this section, we provide a general metaphysical framework for intentional phenomena (i.e., acts or states of thought directed towards an object). To this end, we return to the work carried out at the interfaces between psychology, metaphysics and semantics in the Brentanian school. We start by recalling the bases of Brentano’s doctrine of intentionality (§ 2.1). We then present the developments provided by Twardowski (in particular his theory of the “representation object” (§ 2.2)) and describe how the latter differs from the theories of the intentional object developed by Husserl and Meinong (§ 2.3). Lastly, we specify the metaphysical and semantic commitments linked to our adoption of Twardowski’s representationist theory (§ 2.4).

2.4. Our commitments

In order to build our epistemic ontologies, we thus choose to start from Twardowski’s representationist theory of intentionality. In this section, we specify our metaphysical framework of reference before defining our concept of epistemic ontology.

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Fig. 3.

A metaphysical schema of the act of thinking about an object.

Figure 3 summarizes the entities involved in an act of (abstract) thinking about an object. The subject’s consciousness is directed towards an object immanent to thought (rel IMM). This intentional immanent object is the object of a representation, characterized by a set of properties – the content of the representation. When the subject conceives this object as transcendent to his mind, he conceives the object as representing an external entity (rel REPR) to which he refers (rel REF). The entity transcending the subject’s mind can be physical or mental (and more specifically social since it is thought of by other subjects). In the case where the object is conceived as not representing a transcendent entity, the aiming stops at the immanent object (the dotted arrows in our diagram mean that the corresponding entities need not exist). Figure 3 explicitly shows three of the four terms in the Twardowskian model of the act of thought: the representation object, the representation content, and transcendent entities. The Figure should be seen as a global representation of the fourth term, i.e. the act of thought itself. It should also be noted that the mechanisms of representation and reference are identical in cases where the subject thinks about an object immanent to his mind, for example when his representations in turn become objects of (meta)-representations. The term “conceive” we have used reflects the fact that the representation object is anchored in the subject’s belief system (it is therefore the result of an existential judgment in Brentano’s sense). To account for this epistemic dimension, we use the terms “representation object” and “knowledge object” synonymously in the remainder of the text.

This theory of intentionality leads us to adopt metaphysical and semantic theses distinct from those adopted by today’s foundational ontologies (cf. theses (MT) and (ST) that we recalled in § 1). In particular, on a metaphysical level, we adopt the following thesis (MT)’:

(MT)’: singular and general knowledge objects exist; these allow conscious subjects to represent singular and general aspects of the world.

The knowledge objects in question are the representation objects, as characterized by Twardowski. As we saw in § 2.2, the latter include singular objects and general objects. It should be noted that in addition to objects, we consider other mental entities: properties/relations and propositions. In the present article, we shall not go further into the nature of these entities. However, we draw the reader’s attention to the fact that if properties/relations are considered to be constituents of mental contents, these constituents must also be conceptual and mental in nature.

The objects are endowed with properties corresponding to the content of the representations or (to use a Meinongian term) their “being-such”: the object is such that it bears such and such a property. The lion in general is a carnivorous mammal with a fawn-colored coat. The singular lion Simba is a young male lion (i.e. with a mane) and weighs 150 kg. It is important to note that these attributions of properties stem from psychic acts which for a subject amount to a representation of knowledge about the world. This explains why these objects may be indeterminate with regard to carriage of a specific property, including physical property. The principle of excluded middle (according to which ‘For all F, the object carries F or not F’) does not apply. These objects are incomplete (to use a Meinongian term once again). The Simba object – the knowledge object, not the concrete living object in Africa – may not have any age-related properties (e.g., is it less than three years old or not?). Furthermore, it should be noted that some types of properties cannot be beared by the object. Since Kant, it has been accepted that the predicate ‘to exist’ does not correspond to a property of the object. It does not play the same role as ‘being red’, ‘being round in shape’, ‘being made of wood’, etc. In the Meinongian school, this intuition led scholars to distinguish between nuclear and extra-nuclear properties. This distinction has been defined in a number of ways.28

²⁸

As shown by Nicolas Griffin’s (2017) historical study covering the writings of Meinong up to the contemporary conceptions of the Neo-Meinongians (such as Edward Zalta).

Our interpretation is that nuclear properties relate to the knowledge object by determining it (and thus distinguishing it from other objects, in particular), while the extra-nuclear properties (e.g., ‘to exist’, ‘to be co-referential with’, and ‘to be incomplete’) deal with representation itself, playing in turn the role of knowledge object (the subject judges, for example, that one representation is co-referential with another).

It can be seen that (MT)’ concerns only the domain of the mind. In previous work dealing more specifically with the nature of processes and events (Kassel, 2019; 2020), we were led to make some general commitments. This is notably the case for (MT_i)’ and (MT_ii)’ below, which complement (MT)’:

(MT_i)’ – Each ‘entity’ (a term that we mean to indicate existence), whether physical or mental and with the exception of space and time, is in time.

This thesis consecrates a partition of the world into physical and mental entities. This partition excludes the atemporal Platonic ideas and leads us to consider that both fictitious entities (e.g., mythological entities and characters in novels) and ideal entities (e.g. numbers and geometrical figures) are mental entities (social entities, more particularly).

(MT_ii)’ – Each entity is a particular.

This thesis means that we adopt a nominalism of universals. As mentioned above, universals were introduced historically to explain similarities between entities in the world. Thus, the resemblance between (for example) human beings or sparrows is explained by the fact that an identical universal (‘human being’ or ‘sparrow’, respectively) is present in each individual of the same type.29

²⁹

The universal we have just described is the Aristotelian universal, of which David Armstrong (1997) is one of the most fervent contemporary defenders. For Plato, the universal is an ideal entity floating above objects and being pre-existent to them.

The question of the existence of universals started with a quarrel that can be traced back to the 11th century and continues to be debated in contemporary metaphysics.30

³⁰

As Claude Panaccio (2009) shows in his meticulous investigation.

We choose to refute the existence of universals, for the following reason. Twardowski’s theory of general objects makes it possible to account for the resemblance of singular objects at the mental level by assuming that general objects account for determinations shared by pluralities of singular objects and are (mereologically speaking) repeating parts of individual objects. Of course, this mentally conceived resemblance must have a counterpart in the physical world; however, the parsimony principle tells us not to introduce a new entity unnecessarily – especially a confusing entity that repeats itself identically in many other objects.31

³¹

An analogous strategy in the philosophy of resemblance is defended by Gonzalo Rodriguez-Pereyra (2002).

Let us now turn to our basic semantic commitments with the thesis (ST)’:

(ST)’: terms expressing common sense beliefs or scientific theories refer indirectly to domain entities; the reference is mediated by immanent objects in thought.

In his 1894 essay CO, considering a dialogue between two interlocutors, Twardowski gives three functions to the noun. One locutor’s use of a noun indicates that he/she is presenting something to him/herself – he/she is carrying out an act of presentation. In return, the interlocutor performs a psychic act of the same type – he/she confers meaning by activating a representation associated with that noun. The hypothesis is that to ensure good communication, the two interlocutors are referring to the same extramental entity. This hypothesis is due to the third function of the noun: that of identifying entities (e.g., people, places, and organizations, for proper nouns) and thus ensuring that we can speak of the same entity. Concerning the relation between content and referent entity, Twardowski moreover notes that “mutual” representations with different contents can refer to the same entity (e.g., [the winner of the battle of Jena], [the loser of the battle of Waterloo]).

The relations between content and referent entity that we have just mentioned correspond to the exploitation of a 3-term model of the act of representation (act / mental content / extramental entity). This triadic model evokes the Fregean semantic triad (expression / meaning (Zinn) / reference (Bedeitung)), which makes it possible for several meanings to be coreferential. We should bear in mind, however, that the Fregean meaning corresponds to a Platonic ideality. In fact, the triadic model is closer to the semiotic triangle of Ogden and Richards (1923). These authors placed the act of reference at the core of their semantic theory; their triadic model (symbol / referent mental idea / referent extramental thing) was aptly named the “triad of reference” or (in its graphic presentation) the “triangle of reference”. This model corresponds to the coupling of two causal relations of reference: the symbol (e.g., a noun) evokes an idea in the subject’s mind; in turn, the idea evokes an extramental entity. The referent of any symbol is therefore mediated by an idea.

Let us now place ourselves within the framework of a 4-term model of the act of representation (act / mental content / mental object / extra-mental entity) and consider its contributions. As a preamble, it should be noted that the distinction between singular objects and general objects is in line with the current use of nouns: proper nouns name individual objects, while common nouns name general objects.

Taking account of the representation object first provides an epistemic advantage: a subject may not know that some of his/her representations are mutual, in which case information like ‘the winner of the battle of Jena’ = ‘the loser of the battle of Waterloo’ will extend his/her knowledge system by introducing a coreference relation between these objects or by merging them. Moreover, taking account of the representation object and combining it with other elements sheds light on the hypothesis of reference to the “same” entity by two or more interlocutors. These other elements were provided by Saul Kripke’s (1980) theory of a causal chain of attributions of social properties. This chain begins with a baptism – for example, the individual Aristotle is named “Aristotle” – and this reference is then shared between people and perpetuated from one generation to another. An analogous chain holds for the common nouns conventionally assigned to general objects. Returning to the proper noun, a community of speakers ensures that it refers to the same entity by attributing the same social property of nomination to the object or objects representing Aristotle. The noun is a description, that is a linguistic expression whose meaning corresponds to the properties of an object, allowing it to be referred to and thus identified. More generally, descriptions can also use properties other than the noun to refer to entities – for example, Aristotle could be identified (depending on the subjects’ level of knowledge) as ‘the disciple of Plato’, ‘the preceptor of Alexander The Great’ or ‘the author of Metaphysics’.

Let us now turn to the methodological principle underlying our notion of epistemic ontology:

(MP)’ – Ontological categories correspond to general knowledge objects; the role of ontologists is to identify and organize them by means of generality links.

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Fig. 4.

Outline of an epistemic foundational ontology.

An epistemic ontology (like the one shown in Fig. 4) is thus a system of knowledge representations. More precisely, an epistemic ontology is a taxonomy of general knowledge objects, as indicated by the root Knowledge object. More broadly, an epistemic knowledge base is a set of general objects (an ontology) supplemented by singular knowledge objects, e.g., Paul, Living room table, Displacement of the living room table, representing the way a subject conceives a singular individual of type Person, Table and Event. It is important to note that no representation category directly represents a concrete physical object. To account for the fact that a thought physical object represents an existing object, the property of existence is attributed to the representation (e.g., Rep _Paul ) instance of the general object Representation. This representation has for representation object the singular object Paul which is further characterized by properties attributed to it (the representation content): ‘Paul is a person, is 40 years old, has Mary as a friend’. To better understand the content of an “epistemic knowledge base”, we’d like to add a few details.

As a first point, we emphasize that an epistemic knowledge base, while relative to one subject, makes it possible to account for knowledge objects thought about by several subjects. Work on mental files in philosophy of language and mind assumes that subjects have not only their own mental files, but also files that they attribute to other subjects (Recanati, op. cit.). For example, considering a statement such as “Mary told Paul that she hates Peter”, an explanation in terms of Mary’s and Paul’s informational systems consists in assuming that (i) Mary has a representation of Peter, e.g.: ‘Peter is proud, unpleasant, etc.’; and (ii) Paul has both a representation of Mary and a representation of how Mary represents Peter to herself. In terms of an epistemic knowledge base (ii) amounts to considering that Paul maintains a representation Repr[Paul] _Mary having for object Mary[Paul] (we index in square brackets the representation by the subject that maintains it) but also a representation Repr[Paul] _Peter[mary] of the way Mary represents Peter to herself. With these examples, we simply wanted to evoke the scope of an epistemic knowledge base. Developing such a model of multi-subject representations, however, is beyond the scope of this article.

Secondly, we’re referring to the fact that subjects, while having private representations, possess common knowledge that they acquire and share by communicating with each other. This knowledge, corresponding to the contents of knowledge objects, is both common-sense knowledge (due to the fact that we interact with the same physical world) and, depending on the subjects, scientific knowledge. As the role of ontologies in Applied Ontology is to act as reference conceptualizations for user communities, we amend our principle (MP)’ by specifying that the role of ontologists, beyond identifying shared knowledge objects, is also to identify the knowledge shared by said user communities. Furthermore, in the introduction to this article, we pointed out the specific role of foundational ontologies in helping to structure application ontologies. We can transpose the same requirement to epistemic ontologies, namely that the distinctions made for abstract categories should be based on established principles of metaphysics. In this sense, we have defined the outline of a foundational epistemic ontology shown in Fig. 4. At the first level, the distinction between Physical object and Mental object confirms our thesis of a bipartition between physical and mental entities (MT_i)’.

In the following sections, we deepen our metaphysical framework, which is defined and constrained by the above-mentioned theses (MT)’, (MT_i)’ and (MT_ii)’. We have chosen to focus on the physical world and our knowledge of it, with the ambition of considering both its static and dynamic aspects. This will lead us to address the domains of objects, processes and events. The dogmatic introduction of a partition of worldly entities into mental and physical entities raises a challenge: case-by-case studies (depending on the entity’s domain) of what belongs to the physical world or, in contrast, to our knowledge of the physical world. This is what we will do in the remainder of this article by investigating technical artefacts (§ 3), material qualities of physical entities (§ 4), and events (§ 5). These considerations prompt us to sketch out the epistemic foundational ontology presented in Fig. 4.

We shall begin our study with artifacts, given the strategic role they play in positioning the boundary between the physical and the mental. Like John Searle (1995), we consider that the notion of artifact is based on the attribution of a function to an entity, and that this attribution corresponds to the first step in the construction of social reality. In fact, we need to distinguish between two categories of social entities.32

To illustrate the treatment of artifacts, let us take a “surgical knife” or “surgical scalpel” (in French: “bistouri”) and a “dissecting scalpel” (in French: “scalpel”) as examples. Knowing that these artifacts correspond to identical physical objects, the conceptual distinction that we retain is functional and depends on the context of use: surgical scalpels are used to cut living tissue while dissecting scalpels are used to cut dead tissue.

On an ontological level, let us specify which entities exist in the situation, for example, where a physician uses a surgical scalpel. The theory of representation objects leads us to distinguish two entities: the physical object on one hand, and the representation object corresponding to the conceptualization of the physical object by the physician on the other. A singular representation object Surgical knife _{# i} is thought by the physician as being both a physical object and an artifact (it combines the properties) and this object represents a physical object. If the physician were to use the same object as a dissecting scalpel in a different context, we would have a new Dissecting scalpel _{# j} object representing the same physical object. This situation is illustrated in Fig. 6.

In an epistemic ontology and knowing that a category corresponds to a general representation object, we find the categories Surgical scalpel and Dissecting scalpel as more specific to the category Physical object (cf. Figure 5). The latter, it should be remembered, represents our general knowledge of physical objects.

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Fig. 5.

An ontology of technical artifacts.

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Fig. 6.

The singular objects surgical knife _{# i} and dissecting scalpel _{# j} represent a same physical object.

The situation in which a physician conceives the same physical object in turn as a surgical and a dissecting scalpel is illustrated in Fig. 6. The singular objects Surgical scalpel _{# i} and Dissecting scalpel _{# j} are instances of the general objects Surgical scalpel and Dissecting scalpel

An important point to note about our ontological commitments to physical objects is that we don’t distinguish, on the side of the physical world, a sub-domain of artifacts. In fact, we consider that artifacts are distinguished from non-artifacts not by their physical properties but by other properties – functional ones, in this case. The Technical artifact category accounts for this distinction at the cognitive level. In other words and referring to the theory of levels mentioned in the Introduction, the artifact does not complete the chain of atom-molecule-cell-organism levels according to a homogeneous relationship of constitution. The existing relationship between mental objects conceived as artifacts and material entities in this chain is the relationship of representation.

This question of whether artifacts are physical or mental is key in the recent exchange between Smith and Searle (2003) concerning Searle’s theory of social reality. Searle clarifies his conception of social objects in general as follows (ibid., p. 302):

The notion of a social object seems at best misleading because it suggests that there is a class of social objects as distinct from a class of non-social objects. But if you suppose that there are two classes of objects, social and non-social, you immediately get contradictions of the following sort: In my hand, I hold an object. This one and the same object is both a piece of paper and a dollar bill. As a piece of paper it is a non-social object; as a dollar bill, it is a social object. So Which is it? The answer, of course, is that it is both. But to say that is to say that we do not have a separate class of objects that we identify with the notion of social object. Rather, what we have to say is that something is a social object only under certain descriptions and not others ( … )

We have one reservation and one objection with regard to this conception. The reservation is that Searle conceals the social objects described as being abstract by Thomasson (op. cit.) and for which descriptions do not occur directly on concrete objects. The objection concerns the treatment of concrete social objects. Although we agree that the subject holds only one physical object in his hand – a piece of paper – we hold that the subject’s consideration of the physical object as carrying non-physical properties corresponds to the existence of another object (a mental object this time) – a dollar bill. According to our conception, representational objects representing physical objects carry both physical and non-physical properties and some of these attributions of properties or mental facts acquire the status of social facts by being shared by a community of subjects. This is the case for an artifact such as a surgical knife because a community of subjects attributes to their general object Surgical knife (so named) the function of incising the body of the living.

In Applied Ontology, if we take as a reference the treatment of artifacts by DOLCE and BFO, we find that the non-physical and purely conceptual dimension of the function is not taken into account, to the point of identifying the artifact, as we propose, with a mental entity. In DOLCE, the artifact is identified with a physical object to which an agent assigns a specific capacity.35

We continue our study of the value of making room in our ontologies for mental knowledge objects by tackling the domain of material qualities of physical objects – color, mass, temperature, texture, shape, etc. In fact, we argue that it’s better to speak of two sub-domains, one mental, the other physical. To demonstrate this, we undertake a cognitive reading of the theories of “particular properties” or “tropes” as elaborated by its founding fathers (notably Donald C. Williams and Keith Campbell). We then compare this analysis with recent data from the color sciences, in particular the psychology of perception, which we extrapolate to material perceptible qualities in general. This leads us to consider that the “qualities” constituting a judgment expressed by a sentence like “this car is red”, namely the color of the car that we conceive as inherent to the car, corresponds to a model of physical reality rather than physical reality itself.

According to the standard theory developed by Williams (1953) and that was taken up by Campbell (1980), tropes are properties that depend specifically on their bearer (i.e. they cannot be exchanged between bearers). It is this redness of a rose, this hardness of a piece of metal, this sweetness of a lollipop, this triangularity of a cookie, etc. A common point of the theories is that tropes (or at least those corresponding to certain material qualities) are the immediate objects of perception. This point is important because it underlines the influence of perception and more generally of cognition in the establishment of the abstract character of tropes, as Williams points out in a psychological analysis (ibid., p. 176).

Among the many processes called “abstraction” only the most primitive quite deserves the name: the distinct awareness of the abstractum itself which occurs at the sensory and even the animal level. Hardly higher is a rudimentary generalization, the propensity to treat similar abstract similarly; but the offices of conception are needed for awareness either that a given abstractum is abstract (and belongs to a concurrence sum) or that it exemplifies a universal (an belongs to a similarity set).

By referring to abstraction and generalization as psychic acts, Williams explicitly invokes the conceptual level and emphasizes its determinant role in characterizing the nature of tropes. This makes it legitimate to consider (according to our metaphysical framework) that abstract particular properties are knowledge objects representing physical phenomena. In any case, this is tantamount to considering that trope theory conjures up both the physical and mental levels.

In contemporary, multidisciplinary studies of color (in physics, physiology and psychology), one finds analyses that cautiously distinguish between the physical and mental levels. In their benchmark article (2003) Color realism and color science, Alex Byrne and David Hilbert formulate the following proposition. During a true experience of viewing an object, one can distinguish between two “colors”:

Physical color corresponds to the characterization of the trope as a concrete particular independent of context and thus persisting in the object. Byrne and Hilbert make physical color a dispositional property by defining it as “the proportion of incident light the object is disposed to reflect at each wavelength in the visible spectrum” (ibid., p. 9). Phenomenal color corresponds to the characterization of the trope as an abstract particular. One can consider that it corresponds to the notion of quale (qualia in the plural) used by philosophers to refer to the phenomenal aspects of our mental life.37

We therefore agree that we are dealing with two qualities, one physical, the other mental. We will now clarify the respective roles they play in a judgment involving a quality such as (1a).

Semantically, (1b) indicates that the meaning of (1a) corresponds to an existential judgment of an affair (according respectively to the Brentanian and Twardowskian notions presented in § 2). To resume Twardowski’s analysis: the principal object of (1a) is neither the particular car, nor the particular quality of color, but the affair ‘the being red of the car’ whose existence is asserted. The affair is technically a complex object made up of a simple object corresponding to the car and a simple object corresponding to the car’s color quality – Red_Color _Car . As for the nature of this entity, we opt for the phenomenal color, for several reasons.

The first reason has to do with the nature of perception as evidence for a judgment such as (1b). Like Byrne and Hilbert (ibid.), many philosophers of perception support intentionalist or representationalist theses, according to which perceptual states have a content that relates to the world.38

The second reason reinforces the first and relates to science explanations of the physical realities at the origin of our percepts of quality. For many qualities attributed to a physical object, these explanations call on 1 : n relationships with lower-level entities (according to the theory of levels of material reality mentioned in § 1) constituting the said object: a body’s temperature depends on the movements of its molecules or atoms; the fluidity of water depends on the geometric organization of the water molecules associated with molecules of other substances; the smell of an object depends on the hundreds of thousands of particles emanating from the object and that bind to receptors in our nasal mucous membranes. Temperature, fluidity, odor, etc. are all part of our representations of the physical world. In fact, the statement whereby perceptual qualities “inhere” in their bearer (in the sense that they are in their bearer) illustrates the limitations of our common-sense knowledge.

A third reason relates to the importance of distinguishing between two distinct acts in perceptual judgment carried out by two distinct subsystems, namely perception and judgment. Both are abstract acts of constructing a model of the world, although the abstractions achieved differ in nature. Perception uses intermediate, non-conceptual, sensory representations to produce conceptual percepts. Taking the example of color again, these sensory representations discriminate between thousands of shades that are abstracted into a conceptual percept among the hundred percepts currently available to any subject. Judgment then seizes these conceptual percepts and pursues the abstraction. At this level, a subject can decide to consider that a car is red even if some parts of it (probably those considered to be less important) are of another color. Similarly, based on a thermometer reading, a subject may consider that a room is of a certain temperature even when the room contains several air masses with different temperatures.

For all these reasons, we propose identifying the material qualities of physical objects and their magnitudes with representational objects. The latter represent dispositional properties of physical objects. Thus (cf. Figure 7), the singular object Color _{# i} inherent in the singular object Apple _{# j} represents a disposition giving rise to a process of reflectance of ambient light on the object existing in the physical world.

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Fig. 7.

The fact that material qualities are inherent in a physical object corresponds to a model of the physical world.

The Color object is a general representation object. In the ontology (cf. Figure 8), the Color category is of type Physical object quality. Note that the qualities of physical objects and processes are distinguished.

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Fig. 8.

Ontology of physical entities and their qualities and magnitudes.

This ontology of qualities can be extended in several directions. In particular, it is possible to recognize complex qualities made up of simple qualities, like a color made up of a hue, a brightness and a saturation. It is generally accepted that these primary qualities represent distinct physical phenomena: a wavelength for the hue, a luminance for the brilliance, and a purity for the saturation. Moreover, as suggested by Nicola Guarino (2013), applications may require the consideration of global and local qualities of an object or may even require more detail by considering fields of qualities.40

To finalyse our study, in this section we address the dynamics of the physical world. To account for this, we are about to use processes as well as physical states of affairs. We also use events, but rather than having them play a direct role in the dynamics of the world, we consider them to be mental entities that account for the history of these dynamics. In this way, we show that, as objects of knowledge of the world’s evolutions, events illustrate – particularly – the contribution of an epistemic ontology.

The notions of dynamicity and change are closely linked. Commonly in metaphysics, temporal change on the scale of an object O is characterized by the fact that the object bears a property at one time and a different property at another time: O is F at t and O is F ′ at t ′ . Let us take a closer look at the dynamics of the physical world. An elementary temporal physical change (on the scale of an object O) can be characterized by the fact that a quality Q of O has a magnitude M at t and M ′ at t ′ . However, following the commitments we have just made with regard to the nature of material qualities, this type of characterization corresponds to our (common-sense) knowledge of physical change. Hence, to ensure that we capture a mind-independent dynamic of the world, rather than speaking of “qualities”, we go back to the use of the term “physical property”.

Distinguishing the physical from the mental is precisely what we set out to do in previous work aimed at clarifying the nature of entities described as “occurrents” and which led us to identify three main entities (Kassel, 2019; 2020). On the physical level, processes are enacted by objects and are causally responsible for changes in properties carried by the objects. Again, on a physical level, these changes in properties correspond to homogeneous instantaneous facts that follow each other in time. On the mental level, subjects construct events that reflect the history of these evolutions. Thus, in the physical world, we recognize the existence of a dynamics of objects (but also of processes) that is independent of all thought. Now on the mental level, we situate narration as the main source of (abstract) knowledge of the dynamics of the world. By “narration”, we mean a cognitive activity that consists in selecting a set of facts in a spatiotemporal region and then abstracting them into an event (such as a fight, a shipwreck, a conference, or a revolution). In this section, and after briefly summarizing our characterization of these entities, we discuss the epistemic role and the semantic behavior of events.

As a reminder of our commitments concerning these entities, let us consider the emblematic example of continuous movement (as a kind of spatial change) defined by Bertrand Russell (1903) as follows: “Motion consists merely in the occupation of different places at different times”. According to Russell, the continuous movement of an object O is nothing more than a series of facts corresponding to the occupation Loc by the object O of different positions Pos i at successive instants I j : ⟨ Loc , O , Pos 1 , I 1 ⟩ , ⟨ Loc , O , Pos 2 , I 2 ⟩ , …

Let us summarize the limitations of this conception (which led us to the introduction of the process) and our characterization of the physical process.41

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Fig. 9.

The walkk_#I event represents a series of location facts existing in the world at successive instants.

As mentioned above, the thesis of the existence of the physical process makes it possible to account for the fact that a moving object passes from one state to another, i.e. the dynamics of movement. This being so, we still have not done justice to the existence of movement per se, movement to which we attribute the property of having lasted a certain period of time. The question of the mode of existence of movement, and of change in general, then arises. Change is commonly defined as a kind of event and (as we indicated above) we attribute a mental existence to events.43

In the rest of this section, we shall provide further details of the nature of events.

By considering the example of a state of color (which we consider to be a kind of event) in the previous section (§ 4), we revealed our first commitments to these entities. We thus identify events with knowledge objects – more precisely Twardowskian affairs – that also play the role of objects of existential judgments. In the case of an event e, a judgment has as its content the proposition [e occurs]. For an event, to occur means intuitively that the event happens, in the sense that facts exist by which this occurrence can be judged. The event ‘sinking of the Titanic’ is not only an idea of thought; facts intervened and enable one to judge that the event took place.

Let us specify the mode of knowledge of events when the latter are constructed from a perception of the world. The field of temporal perception – that is the ability of perception to deal with the passage of time – has been extensively studied. Here, we retained Christopher Peacocke’s theory (2019) for the emphasis put on the metaphysical dimension.44

So far, we have given a broad range of illustration examples of events. Although it is possible to classify these events schematically into two main species (states and changes, depending on whether stabilities or transformations of the (physical) world are narrated), these events vary significantly according to the spatiotemporal region and facts involved. Based on the size of this region and the number of facts considered, we can distinguish between simple events involving a small number of physical entities (objects and processes) and complex events involving a multitude of entities. We can cite the following examples, in the order of increasing complexity: a hug between two people, a fight involving a group of people, a seminar, a shipwreck, and a revolution. To this complexity of events corresponds a complexity of judgments of existence, which we will not attempt to characterize in the present article. We would have to introduce a mereology of events and define a salience of facts to account for their relative importance in the identification of an event. In contrast, for simple events, it remains possible to identify approximately the occurrent-maker facts to be taken into account by a subject. Below, we give some examples of occurrence judgments of simple events involving processes and that illustrate their semantics.

The judgment expressed by (2a) can be assimilated to an occurrence judgment of a walking state of Paul (2b) – such a state corresponds to the Walk _{# i} event shown in Fig. 9. The occurrence of this state is due to the fact that Paul enacts (is the seat of) a walking process (2c) – this Walking _{# j} process is to be distinguished from the Walk _{# j} event. The judgment expressed by (3a) corresponds to the judgment of the existence of a speed state for Paul’s walking process (3b). The occurrent-maker facts are facts corresponding to the inherence of a speed quality with a rapid magnitude in the process (3c). Lastly, (4a) expresses a judgment of the occurrence of a more complex event involving both a process enacted by Paul Proc # i (the type of which is not specified), a movement process enacted by the table Move _{# j} and a causal perpetuation of one process by the other.

Note that the series of facts (i.c) {Fact1, Fact2, …} correspond to finite sets. Their cardinality depends on the facts taken into account by a subject to decide on the occurrence of events (i.b). In contemporary metaphysics, the existence of such physical facts is questioned, on the pretext that they are made up of entities of a hybrid nature, i.e., a universal relation and particulars. For our part, we justify the existence of these facts by considering that the terms ‘Loc’, ‘Enacts’ and ‘Perpetuates’, usually designating relations, represent in this case particular physical phenomena connecting properties to their bearer.45

In summary, and on the ontological level, a unique singular thought event (regardless of its complexity) finds itself representing a multitude of facts. Take the example of an impersonal statement like “it is raining”, for which the endless explanation advanced for veracity is “it is true that it is raining because it is raining”. The second occurrence of “it is raining” refers to a concrete Davidsonian event. What one gains by mentalizing the event is a more intuitive explanation of a judgment based on the existence of a multitude of drops of water falling: “it is true that it is raining [‘a rain’ occurs] as many drops of water are falling”.

In this paper, we have defined a type of conceptualist ontology called an epistemic ontology. The latter’s categories correspond to general knowledge objects representing the world. We have also developed a metaphysical framework for the development of epistemic ontologies. By opening our inventory of the furniture of the world to the mind and taking care to distinguish rigorously between the physical and the mental, this framework turns out to be different from those of common foundational ontologies. It illustrates a nominalism of universals and platonic ideal entities. Moreover, by identifying events with mental entities, the framework supports a new epistemic thesis, that stabilities and changes are parts of the history of the world but are not in the world as it unfolds. Lastly, an epistemic ontology is an ontology of temporally enduring particulars. The distinction between endurants and perdurants present in BFO and DOLCE is no longer relevant. This is essentially due to the fact that events are conceptualized as mental endurants.

The question of the value of the metaphysical framework then arises. In this respect, we have tried to show that the framework aggregates established metaphysical theses that are consistent with contemporary data in psychology especially that of psychology of perception. These metaphysical theses are not in the mainstream of contemporary metaphysics (notably with respect to their openness to the mind) but we do not draw any conclusions from this concerning their value. Furthermore, the question of the boundary between the mental world and the physical world continues to be on the records of contemporary metaphysical research. Above, we mentioned the example of events. One can also raise the question of the existence of a macroscopic physical world that is independent of the mind, as defended by Petitot and Smith (1996).

On a practical level (for the development of ontologies), we have shown (particularly with our treatment of artefacts) that the notion of a “knowledge object” allows us to attribute both physical and social properties to objects representing the physical world. In this case, the social properties of technical artifacts are functional properties related to the use of these objects. We note that this possibility legitimizes a common practice among ontologists, who do not ask themselves theoretical questions about the existence of universals or general knowledge objects. At the same time, the diversity of properties that can be attributed to a knowledge object raises the question of the criteria used to structure these object classifications and to elaborate classifications that are consensual – especially in scientific fields (Sterner et al., 2022). The question of whether or not the principle of “ontological realism” (i.e. giving priority to physical properties) should be adopted is as relevant as ever.

Regarding consensual classifications, we would like to highlight a contribution of epistemic ontologies that we consider to be fundamental. Since knowledge objects are representations of reality, it is possible to consider several objects that correspond to different representations of reality. Sterner et al. (ibid., p. 241) give the example of the development of ontologies of anatomical parts where distinct criteria (evolutionary homologies and structural similarities) can be taken into account and can sometimes give rise to inconsistencies. Given the representational nature of knowledge objects, it is possible to consider objects that describe reality according to distinct theories – even if it means specifying that these objects are co-referential. In our opinion, this possibility may account for a strong, current trend in the philosophy of biology: the assimilation of living organisms to processes. In other words, living organisms are assimilated to stabilized “dynamic” activities rather than “static” things (cf. (Dupré and Nicholson, 2018; Skrzypeck, 2023)). This conception corresponds to scientific metaphysics of living organisms that is co-referential with the common-sense metaphysics we have favored in this article.