1 Ontology: Navigating the Fundamental Categories
Philosophical ontology was traditionally characterized as the disciplined pursuit of unraveling the very essence of existence itself, overlapping, at least in part, with metaphysics (Hofweber, 2020; Varzi, 2011). Traditionally, it probed into the systematic exploration of “being,” trying to shed light on the fundamental categories that underpin our reality and taking the shape of what can be termed as the “tree of being,” a hierarchical representation of the fundamental aspects of existence. More recently, the evolution of ontology has seen the emergence of dynamic flux diagrams, which visually illustrate the hierarchy of generality and the intricate web of relationships among categories and their subordinated classes that branch from the fundamental kinds of entities (Hoffman and Rosenkrantz, 1994; Chisholm, 1996; Smith, 1998; Koepsell, 1999; Gangemi et al., 2003), sometimes under the shape of a formal description (as in the formal outline of a program) of the concepts and relations allowed within a language (Gruber, 1993; Guarino et al., 1994; Smith, 2003). At its core, contemporary ontology serves as a meticulous specification of our categories, presenting them in a structured manner (Smith and Medin, 1981; Valore, 2016).
As we venture further into the field of ontology, a question naturally arises: How do we go about correlating individuals with these fundamental ontological categories? Given that the bridge between individuals and ontological categories is constructed through a process of classification and categorization, our ontological inventory seems an endeavor akin to placing each unique puzzle piece into its designated slot, forming a coherent picture of the world. This process seems to require a keen understanding of the attributes, characteristics, and essential qualities that define both the individual entities and the overarching categories.
2 The Challenge of Resemblance and Property Sharing in Ontology
One of the simplest and most intuitive ways to approach ontology is by drawing connections based on resemblance. In this framework, certain entities are seen as bearing a resemblance to others, forming a foundational understanding of their categorization. This concept of similarity can be further elucidated through the lens of property sharing—a notion that suggests entities are grouped together when they share certain essential properties.
However, despite its initial appeal, this approach to ontology is not without its complexities and challenges. As Immanuel Kant already pointed out in the First introduction to The critique of the power of judgment (Kant, 1790/2002, pp. 15–16), a profound issue lurks within this seemingly straightforward account:
Logic […] teaches how one can compare a given representation with others, and, by extracting what it has in common with others, as a characteristic for general use, form a concept. But about whether for each object nature has many others to put forth as objects of comparison, which have much in common with the first in their form, it teaches us nothing; rather, this condition of the possibility of the application of logic to nature is a principle of the representation of nature as a system for our power of judgment, in which the manifold, divided into genera and species, makes it possible to bring all the natural forms that are forthcoming to concepts (of greater or lesser generality) through comparison.
The problem that Kant identified revolves around the inherent subjectivity in determining what constitutes a shared property and the degree of resemblance required for categorization. When we embark on the task of identifying essential properties that underpin resemblance, we find logic itself does not inform us how to apply the notion of “having something in common” to what Kant calls “nature” and we can consider any domain of a given plurality that has been ordered in kinds. In fact, if we do not specify what we are looking for, anything can have something in common (“have similar form”) with a number of other things as objects of comparison. What one observer might consider a shared property, another might dismiss as superficial or insignificant. Kant’s insight prompts us to tread cautiously in our ontological pursuits and encourages a deeper exploration into the intricacies of property sharing and the subjective nature of resemblance (see also James, 1920; Husserl, 1900–1901/2001, on the risks of resemblance as a basis for classifications). Nonetheless, clarifying in what sense things have forms in common (where “forms” are, essentially, sortal properties), and therefore belong to the same fundamental category, is required for our understanding of nature as a system. In the definition of ontology given above, we saw, in fact, that we aim at a systematic and consistent representation of individuals classified into genera and species in order to build the hierarchy of generality that is the goal of the discipline.
3 The Quandary of Ontological Reconstruction: Resemblance, Sets, and Predicates
The concept of “resemblance” or “similarity” serves as a natural starting point for any systematic unity of nature. Looking around for resemblances is an approach grounded in our daily observations, where we intuitively group entities together based on their shared characteristics. This process, however, introduces an issue: how can we systematize this intuitive human instinct into a rigorous ontological framework?
One potential solution lies in the reduction of the elusive notion of resemblance into more manageable and structured concepts, such as set membership, which could offer a formal pathway to navigate the complex task of ontological classification. The underlying premise is that by defining sets of individuals and sets of predicates, we can establish a clear, consistent, and systematic connection between them.
Consider, for instance, two fundamental sets: “I,” representing individuals (I1, 2, …, In), and “P,” representing predicates (P1, P2, …, Pn). For each individual Iᵢ, we could pair an appropriate predicate, either Pᵢ (indicating that the individual possesses a certain property) or not-Pᵢ (signifying the absence of that property). This pairing represents a crucial step in determining an entity’s place within the ontological framework.
However, this seemingly straightforward approach encounters its own challenges when faced with the nuanced nature of properties: the assumption that properties do not come in degrees oversimplifies the intricacies of ontology. In reality, properties often exist along a spectrum, complicating the assignment of predicates: the degree of resemblance or similarity can vary, making the task of categorization a multi-faceted and intricate process that cannot always be reduced to a yes or no demarcation. For instance, determining whether an object A conforms to a property P, signifying its alignment with the prescribed criteria or conditions required to establish A ∈ P, might not suffice. The introduction of a notion such as a “degree of satisfaction” or a “degree of fulfillment” transcends a binary conception of possession, acknowledging the spectrum by which properties may be satisfied. Consequently, an object A can be described as possessing a degree of satisfaction or fulfillment with regard to a property P, with a designated level of satisfaction specified.
4 Distinguishing Resemblance: Object-to-Object and Object-to-Kind
Additional complications are also on the way. Upon closer examination, it becomes in fact evident that there are at least two distinct types of “resemblance” at play. For instance, botanists might observe several individual specimens of a particular genus of flowering plants, such as roses, noting shared characteristics such as the arrangement of petals, thorn patterns, and leaf morphology. By recognizing these shared attributes among individual roses, botanists can classify them into the genus Rosa. I call this first form of resemblance “object-to-object” (OtO). On the other hand, ornithologists utilize a different form of resemblance to associate individual bird species with the overarching category of Passeriformes based on shared morphological and behavioral traits, aligning them with the kind of bird they most closely resemble. I call this second form of resemblance “object-to-kind” (OtK).
OtO and OtK resemblances operate in tandem to facilitate our understanding of a given domain of entities. The first type involves the act of grasping or constructing kinds by observing similarities among individual objects themselves. In this process, we draw connections and patterns by directly comparing one entity to another: it is an act of recognition that hinges on the shared attributes, qualities, or characteristics exhibited by individuals. This first type forms the foundation upon which we build our understanding of general cases, resulting from our selective acts of grouping (Valore, 2018).
Having established general cases through OtO resemblance, we can then link other individuals to these pre-established kinds based on their similarity to those kinds. OtK resemblance bridges the gap between individual entities and the overarching categories or kinds they belong to. It is a process of association, where entities are aligned with the kinds they most closely resemble.
The synergy between OtO and OtK resemblance is pivotal in our quest to navigate the intricate web of ontology. By initially recognizing similarities among individual objects (OtO), we lay the groundwork for a structured representation of a given domain. Armed with these general cases, we can then extend our understanding to encompass a broader spectrum of individuals, aligning them with the kinds that resonate with their unique attributes and characteristics (OtK).
With this distinction in hand, we can now uncover a deeper difficulty in our strategy.
5 The Pitfalls of Set-Based Similarity
While our previous discussion considered the challenges of ontological categorization under certain assumptions, such as properties not coming in degrees and the determinability of property satisfaction (which is not always possible), we now confront a more profound issue that transcends these assumptions. This significant hurdle becomes glaringly apparent when we attempt to better refine our previous strategy of translating similarity into set membership. Regrettably, this deeper analysis of our initial translation, rather than clarifying, proves to be fraught with new complications.
We may try to improve our monodimensional initial account, introducing, for instance, notions such as “I1 is more similar to I2 than I3,” defined in terms of “I1 and I2 are joint members of more sets than I1 and I3.” At first glance, translations such as this appear promising, suggesting a quantitative measure of similarity based on shared set membership. However, upon closer inspection, a fundamental flaw becomes evident.
For instance, consider a sociological study examining social circles within a university campus. Let us denote three individuals: Anna, Bob, and Clara. Suppose Anna and Bob are roommates who share similar academic interests and frequently interact, while Clara is a student from a different department whom they occasionally encounter. In this scenario, Anna and Bob should jointly belong to several sets, such as “Roommates,” “Classmates,” and “Study Group Members,” due to their close relationship and shared activities. Conversely, we expect that Anna and Clara share fewer sets, perhaps only “University Students” or “Campus Residents,” reflecting their limited interaction and disparate interests. However, the mere consideration of sets fails to capture the nuances of these similarities: other permutations that may not be considered relevant are still genuine sets and should, in principle, be counted, such as organizing the students based on body mass or other arbitrary characteristics.
The crux of the issue lies in the nature of sets themselves, which are generated blindly, through the exhaustive combination of elements. In fact, the number of sets to which any two elements jointly belong is not contingent upon the inherent features or characteristics exhibited by those elements—in other words, their degree of similarity. Instead, that number is determined solely by the total number of elements within the sets they share (Quine, 1969). This revelation fundamentally disrupts the translation of similarity into set membership as a viable method for ontological categorization: the number of shared sets is not a meaningful indicator of the classes or categories that individuals should rightfully join. But what does “rightfully” mean here?
6 The Need for a Reliable Generating Principle
We encounter here a crucial realization: the significance of a dependable generating principle. This principle serves as our guiding light, illuminating the intricate path of classification and categorization. It is the cornerstone upon which we construct our sense of appropriateness and suitability, enabling us to make choices that harmonize with our predefined objectives and the contextual parameters we establish, if we are interested in natural and not arbitrary kinds (Campbell et al. 2011; Bird and Tobin, 2016; Beebee and Sabbarton-Leary, 2010a).
First of all, it is essential to acknowledge that what we perceive as unwanted or unsuitable choices is contingent upon the aims we set and the context we define: our ontology is not an unchanging framework but a flexible structure that adapts to the specific goals we outline (LaPorte, 2004). Within this fluid and evolving context, it becomes imperative to identify and employ a generating principle that we can place unwavering trust in. This principle empowers us to establish precise criteria for categorization, defining the essential attributes, characteristics, or properties that qualify an entity to be an instantiation of a particular kind or category (Stuart, 2021).
7 The Fluid Nature of Taxa in Classification Systems
Observing our strategies of grouping individuals in categories, it becomes more and more evident that the taxa recognized by various systems are not etched in stone but rather exhibit a dynamic quality, in the sense that different taxonomic groupings can be considered “natural” in different respects, contingent upon the particular background theories and conceptual frameworks that underpin them (Haslanger, 1995; Benitez et al., 2022; Xu et al., 2022; Valore, 2016; Del Pinal, 2016; Valore, 2017b). A way to understand the locality of reason is acknowledging that the very “nature” of what we classify and how we group entities is shaped by the backdrop of our conceptual schemes or categorial frameworks. The background theories we adopt act as the guiding principles we were looking for, determining which structure of kinds or categories we acknowledge over others. In other words, the choice of how we classify the diverse entities that populate our world is intimately linked to the theoretical lenses through which we view them. Empirical evidence reinforces this notion, revealing that individuals engaged in experiments related to categorization and similarity rating produce distinct patterns of classification based on different (sometimes tacit) initial intuitions (Rehder and Hastie, 2001; Ahn and Kim, 2000). This has also been confirmed by studies in cognitive science about the psychology of learning and categorization (e.g., Lalumera, 2010; Hampton and Jönsson, 2012).
8 The A Priori Framework
At the outset of our exploration of ontological categories, the concept of “kinds” led us to hope that the analysis of individual cases in terms of communal properties, when subjected to controlled experiments under identical conditions, would yield consistent outcomes. This consistency should arise from the shared sortal property—whether it be nature, disposition, or essence—that defines these cases as belonging to the same kind. Prima facie, it seems imperative to rely on the notion of intrinsic or relevant properties to discern these shared properties. However, our inquiry has revealed a critical nuance: the concept of a relevant property is not a universally applicable one and it, rather, hinges on the presence of a background theory, a conceptual framework that shapes our understanding of what properties are intrinsic and relevant (to the point that the very meaning of “relevant” may be pluralized). A background conceptual scheme, in essence, serves as the a priori, the foundational premise upon which our ontology is constructed, and it establishes the guiding principles that dictate how we perceive and categorize the world around us. But it is a plural, dynamic, and perspectival a priori. This significantly alters the conventional understanding of “a priori” as defined by Kant, wherein these principles are universally shared by all rational beings like us, implying a single set of principles rather than multiple such sets. However, Kant’s concept of the unique and fixed set of principles that serve as preconditions for organizing a specific plurality could, in a similar vein, be fulfilled by various potential sets of “localized” a priori principles.
In our quest for proper categorization, we are thus confronted with a twofold challenge: first, to recognize the profound influence of our background theory on what we deem relevant properties and, second, to navigate the variable and intricate interplay between these theories and the applications to our data.
9 The Local and Context-Dependent Nature of Presuppositions in Taxonomies
In contemporary ontology, a recent approach has emerged that seeks to illuminate the often-hidden metaphysical presuppositions underpinning our taxonomies and categorizations in the field of science, thanks to tools like conceptual engineering and conceptual analysis (Guarino, 1985; Cappelen, 2018; Burgess et al., 2020; Chalmers and Jackson, 2001; Chalmers, 2020). This innovative perspective, as exemplified by recent works such as those by Xu et al. (2022) and Valore (2016), draws our attention to the fact that our taxonomies are not universally objective systems but are deeply influenced by specific, local, and context-dependent metaphysical presuppositions.
This viewpoint prompts us to investigate the foundational aspects of our taxonomies, unveiling the implicit assumptions and metaphysical underpinnings that guide our categorization endeavors. It is an approach that challenges the notion that a one-size-fits-all algorithmic procedure exists for sorting entities into genera and species, emphasizing instead the intricate interaction between our categorization efforts and the particular aims and options embedded in specific theories. In surfacing and acknowledging these local presuppositions, we gain a deeper understanding of the multifaceted nature of taxonomies. This viewpoint assigns us the task of engaging in a critical examination of how specific theories and contexts influence our categorization processes, without assuming complete relativism.
10 Towards a General Theory of Theoretical Knowledge Embedded in Categorization
In a nutshell, the call for a general theory of the theoretical knowledge embedded in human representation of kinds, types, and categories invites us to explore the intricacies of how we perceive and organize the world around us. This theory challenges traditional notions and underscores the importance of context and perspective in our understanding of categorization. Its main features are the following:
Suspicion of a Single Taxonomy: First and foremost, we should approach the idea of a single, universally correct taxonomy of kinds or a unique grouping of individuals with skepticism. Such a taxonomy, detached from considerations about what constitutes relevant or perspicuous properties, may not hold in diverse contexts and from different perspectives (see the notion of “ontological relativity” in Rosch and Mervis, 1975; Rosch, 1978; Sosa, 1999; Sosa, 2009).
Role of Background Theory: The determination of relevant or perspicuous properties hinges on the presence of a background theory or, better, theories. These theories, intrinsic to our categorization efforts, provide the lens through which we view the world and discern what attributes matter most (see the role of implicit ontological commitments based on couched assumptions in Chihara, 1968; Chateaubriand, 2003). Keeping these presuppositions hidden or being simply unaware of their relevance makes us blind to choices that are not necessarily “natural” in any sense.
Exploration of Alternative Ordering Strategies: In constructing categorizations of individuals using natural kinds, it is crucial to remain open to alternative ordering strategies. Long-standing taxonomies may appear “natural,” yet they can limit our exploration of new perspectives and alternative organizational structures, limiting the most innovative features of our scientific research.
Embracing Metaphysical Assumptions: The selection of relevant properties for guiding our taxonomies should not be marred by condescension toward the disclosure of metaphysical assumptions. Rejecting these assumptions as tarnishing scientific purity is a dated attitude, linked to a neopositivist approach that does not do justice to our actual knowledge enterprise (Quine, 1969). We should, instead, recognize that these assumptions are inherent to our aims and are integral to the formation of our taxonomic frameworks.
Ramifications and Implications: These principles have far-reaching consequences. They influence our pursuit of cognitively adequate ontological representations, the assessment of information sources’ reliability, the impact of interests and preferences on data handling, and the exploration of the rationales behind the selection of relevant concepts in our knowledge-building process.
11 Applications
The concept of background ontological presuppositions finds practical application in diverse fields, where it can significantly impact our understanding and categorization of complex phenomena (Munn and Smith, 2008). We have attempted the application of this approach to two notable cases where ontological relativity seems to play a key role: cosmology (Valore et al., 2020) and biomedical research (Valore, 2017a; Valore and Witzel, 2024; on the notion of “kind of disease,” see also Sulmasy, 2005; Schwartz, 2007; Dragulinescu, 2010; Lemoine, 2013; on the notion of “kind of patient,” see Hadorn, 1997; Beebee and Sabbarton-Leary, 2010b).
In cosmology, the problem of selection in detecting cosmological objects, such as supernovae, galaxies, and gamma-ray bursts, highlights the relevance of significant background ontological presuppositions in defining entities and properties. A compelling illustration is the case of supernovae. Until the mid-1980s, astronomers categorized supernovae into two basic types: Type I and Type II. Type I supernovae were considered similar, and a common progenitor scenario for Type Is was assumed. However, in the late 80s, a shift occurred, revealing that despite their apparent similarities, Type I supernovae were entirely distinct events. This was not determined by new discoveries but by a shift in our focus and in the selection of properties relevant to our definition. Expanding on this case, in Valore, Dainotti and Kopczynski 2020, we underscore the profound impact of background ontological presuppositions on the categorization and classification of cosmic phenomena, such as Gamma-ray bursts.
The application of background ontological presuppositions extends to biomedical research. We tested the theory in cardiology (Valore, 2017a) and ophthalmology (Valore and Witzel, 2024, for the case of glaucoma). In biomedical research, notions like “kinds of patients,” the very idea of a similarity among individuals generating the proper, relevant kinds (OtO), and the similarity between an individual and kinds identifying the proper, relevant kind for that individual (OtK) appear inescapable but obscure. Drawing on a case study of glaucoma surgery and intervention in New York State hospitals, we examine (Valore and Witzel, 2024) how ontological assumptions and conceptual relativity shape medical theory and clinical practice, to the point of affecting diagnosis and medical intervention.
12 Embracing the “Locality” of A Priori Principles in Understanding Nature
The approach we have explored here resonates with a fundamental Kantian insight, as we saw in The Critique of Judgment, and it underscores the pivotal role that aims and purposes (and even values: see Putnam, 2004; Marchetti and Marchetti, 2016) play in our quest to uncover similarity in the natural world and within a given set of data. Such an approach represents a recognition of the “locality” inherent in the a priori principles that guide our understanding of nature.
In essence, the approach we have explored calls us to engage in a more holistic and inclusive dialogue, one that embraces the multifaceted nature of human cognition and the diverse mosaic of our intellectual pursuits. There are various sets of a priori principles of our reason that guide our taxonomies; they are rooted in psychological, anthropological, and cultural dimensions of human knowledge and linked to different interests and goals (what we called here “background theories”). Nonetheless, these a priori principles are not arbitrary and cannot be randomly chosen, as they are linked to consequences in situations or instances that are closely related, with effects that ultimately affect the entire knowledge system. Furthermore, each background set of assumptions come with its list of costs and benefits that need to be frankly discussed and evaluated (and certainly not kept hidden or tacit, let alone presented as “natural”).
Understanding the ramifications of this position can facilitate mutual understanding across theories, research fields, and even generations and communities. In embracing the “locality” of our a priori principles, we come to appreciate the richness and complexity of human knowledge, marking the diverse interests and goals that shape our understanding of the natural world and saving a positive role for our metaphysical intuitions in terms of diversified and relativized a priori principles.
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