Metaphysical grounding is a relation of metaphysical dependence that aims to capture how certain facts or entities obtain “in virtue of” others. It is commonly regarded as a non-causal, explanatory connection between less fundamental and more fundamental elements of reality. Grounding has become a central topic in contemporary analytic philosophy, particularly in discussions of metaphysics, modality, ontology, and the philosophy of explanation. Proponents of grounding argue that it provides a unifying framework for understanding metaphysical structure, including the hierarchy of being, the nature of truthmaking, and the relationship between higher-level and lower-level properties.
To understand what is meant by grounding, consider an ordinary physical object, such as a table, and the atoms it is made of. Without the atoms, the table would not exist; thus, the table's existence depends on the existence of the atoms. This kind of dependence is called grounding to distinguish it from other kinds of dependence, such as the dependence of an effect on its cause. It is sometimes called metaphysical or ontological dependence.
In its paradigmatic form, grounding is used to express claims like: “The fact that the rose is red is grounded in the fact that it reflects light at approximately 700 nanometers,” or “The existence of a set is grounded in the existence of its members.” These are not claims about causation—grounding is taken to be atemporal and non-empirical—but about what metaphysically explains or determines other facts. Take the example of the grounds of natural classification. Here, John Stuart Mill wrote, “In so far as a natural classification is grounded on real kinds, its groups are certainly not conventional; it is perfectly true that they do not depend upon an arbitrary choice of the naturalist." Book IV, chapter II.
Grounding is typically described as a form of determination that is finer-grained than logical entailment and supervenience: it is possible for two propositions to be necessarily coextensive while differing in their grounds.
The modern resurgence of interest in grounding was catalyzed by the work of Gideon Rosen,Rosen, Gideon (2010). “Metaphysical Dependence: Grounding and Reduction.” In B. Hale & A. Hoffmann (eds.), Modality: Metaphysics, Logic, and Epistemology. Oxford: Oxford University Press, pp. 109–135. Kit Fine,Fine, Kit (2012). “Guide to Ground.” In F. Correia & B. Schnieder (eds.), Metaphysical Grounding: Understanding the Structure of Reality. Cambridge: Cambridge University Press, pp. 37–80. and Jonathan SchafferSchaffer, Jonathan (2009). “On What Grounds What.” In D. Chalmers, D. Manley & R. Wasserman (eds.), Metametaphysics: New Essays on the Foundations of Ontology. Oxford: Clarendon Press, pp. 347–383. in the early 21st century. These philosophers positioned grounding as central to understanding a wide array of metaphysical issues, from the status of moral and mental properties to debates about fundamentality and reduction. For example, Rosen characterizes grounding as a primitive relation that expresses the metaphysical analogue of explanation, while Schaffer contends that the proper subject matter of metaphysics is not what exists, but what “grounds” what.
Despite its growing prominence, grounding remains controversial. Some philosophers, such as Jessica Wilson,Wilson, Jessica (2014). “No Work for a Theory of Grounding.” Inquiry 57(5–6): 535–579. have challenged its coherence and explanatory utility. Others, like Karen Bennett,Bennett, Karen (2017). Making Things Up. Oxford: Oxford University Press. advocate for a pluralist framework that includes grounding as one among many “building relations.” The ongoing debate has produced a rich literature on the logic, metaphysics, and semantics of grounding, with increasingly fine-grained distinctions between competing theories.
Core concept and motivation
Dependence “in virtue of” The central idea of metaphysical grounding is that certain facts or entities obtain in virtue of others. In such cases, the grounded depends for its existence, truth, or status on the ground in a way that is metaphysically prior and explanatory. Grounding is commonly treated as a relation between facts or propositions, though some philosophers extend it to include objects, properties, or other entities.Bliss, Ricki & Trogdon, Kelly (2021). "Metaphysical Grounding", in Edward N. Zalta (ed.), The Stanford Encyclopedia of Philosophy (Fall 2021 Edition), https://plato.stanford.edu/archives/fall2021/entries/grounding/. This relation is said to capture a distinctive kind of metaphysical dependence—one that is neither causal nor merely nomological, but constitutive and explanatory in character.
A distinction is typically made between grounding relations and other dependence relations, such as causation or realization. Grounding is often considered to be a form of non-causal determination or priority. Things which are less fundamental are grounded in things that are more fundamental.
As another example, consider the property of being either even or prime. The number 4 has this property because it is even. Here "because" does not express a causal relation (where the cause precedes the effect in time). It expresses a grounding relation. The fact that the number 4 is even or prime is grounded in the fact that 4 is even. In other words, the first fact obtains in virtue of the second fact.
Distinction from causation and supervenience Grounding is generally distinguished from causal dependence. Causation is typically understood as a temporally asymmetric, empirically discoverable relation between events; grounding, by contrast, is taken to be atemporal and non-empirical. For instance, while the melting of ice is caused by a rise in temperature, the existence of a singleton set is grounded in the existence of its sole member. These two modes of dependence differ in directionality, modality, and ontological scope.
Grounding also contrasts with logical entailment and supervenience in being more fine-grained. While grounding implies entailment—if A grounds B, then necessarily, if A then B—the converse does not hold. Necessarily equivalent propositions need not stand in a grounding relation. For example, the propositions "2 + 2 = 4" and "the number of planets in the Solar System is 8" are both necessarily true, but neither grounds the other. This distinction is often framed in terms of grounding’s hyperintensionality: it is sensitive not just to truth-value or necessity, but to the manner in which facts are determined.
Explanation and hierarchical structure Because grounding tracks metaphysical explanation rather than mere entailment, many philosophers regard it as a sui generis relation not reducible to other modal or logical notions. Rosen describes grounding as “the metaphysical analogue of explanation,” and Fine argues that grounding supports a “pure logic of ground” capturing explanatory priority in metaphysical structure.
Grounding is typically assumed to be asymmetric and irreflexive: if A grounds B, then B does not ground A, and no fact grounds itself. These properties give rise to a hierarchical conception of reality, where more fundamental facts or entities serve as the basis for less fundamental ones. This layered ontology is central to contemporary neo-Aristotelian metaphysics, which seeks to articulate not merely what exists, but how what exists is structured in terms of priority and dependence.
According to the neo-Aristotelian approach to ontology, the goal of ontology is to determine which entities are fundamental and how the non-fundamental entities depend on them. Fundamentality can be expressed in terms of grounding. For example, according to Aristotle, substances have the highest degree of fundamentality because they exist in themselves. Properties, on the other hand, are less fundamental because they depend on substances for their existence. In this example, properties are grounded in substances.
Grounding in contemporary debates Contemporary interest in grounding is driven by the need for a systematic account of non-causal explanation. Many philosophers maintain that there are explanatory relations that do not involve causation—for example, the dependence of normative facts on descriptive ones (as in ethical naturalism), or of mental states on physical states (as in physicalism). Grounding has been proposed as the underlying metaphysical relation that makes sense of these forms of dependence.
Jonathan Schaffer has argued that “metaphysics is the science of what grounds what,” proposing that grounding—not existence per se—is the central organizing concept of metaphysical inquiry. This perspective has led to a wide range of applications: from modeling ontological dependence and fundamentality, to explicating reduction, explanation, and truthmaking. On this view, grounding provides not only a relation between facts, but a conceptual tool for understanding the architecture of reality itself.
Historical antecedents
Aristotle and Neoplatonism Although the technical vocabulary of metaphysical grounding is a recent development in analytic philosophy, the core idea—that some entities or truths depend upon more fundamental ones—has deep historical roots. Classical philosophers frequently described reality in terms of ontological hierarchies, where certain beings or truths were considered more basic or prior than others. These antecedents help contextualize contemporary debates, even if they lack the formal rigor or explicit terminology of modern accounts.
In Aristotle’s metaphysics, the notion of what is “prior in being” (proteron tou einai) versus “posterior” anticipates grounding relations. Aristotle holds that substance is ontologically prior to accidents, and that universals depend on particulars for their instantiation. In Metaphysics V.11, he writes: “That which is prior in substance is the cause of what is after in substance.”Aquinas, Thomas. Summa Theologiae, I, q.44, a.1. In Aquinas (2006), Summa Theologiae: A Concise Translation, ed. Timothy McDermott. Allen, TX: Christian Classics. While this language is causal, its function is explanatory and structural rather than temporal. Similarly, the Posterior Analytics develops a conception of scientific explanation that invokes explanatory priority, wherein knowledge of effects is grounded in knowledge of causes.Rosen, Gideon (2010). “Metaphysical Dependence: Grounding and Reduction.” In B. Hale & A. Hoffmann (eds.), Modality: Metaphysics, Logic, and Epistemology. Oxford University Press, pp. 109–135.
Neoplatonism, particularly in the work of Plotinus, elaborates a metaphysical hierarchy grounded in the One. Plotinus’s doctrine of emanation describes all levels of reality as deriving from a single, most fundamental source, with each successive level depending ontologically on the level above it.Plotinus. The Enneads, V.1–V.5. Trans. A.H. Armstrong. Cambridge: Harvard University Press, Loeb Classical Library, 1966–1988. This structure mirrors contemporary grounding models in which higher-level facts are grounded in more fundamental ones. Although the Neoplatonic scheme is metaphysically loaded, it exemplifies the explanatory and asymmetrical character associated with grounding.
Medieval perspectives