Jeroen Smid

Lewis famously argued that mereology is ontologically innocent. Many who have considered this claim believe he was mistaken. Mereology is not innocent, because its acceptance entails the acceptance of sums, new objects that were not previously part of one’s ontology. This argument, the argument from ontological parsimony, has two versions: a qualitative and a quantitative one. I argue that the defender of mereology can neutralize both arguments by holding that, given mereology, a commitment to the parts of an object is not an extra ontological commitment, made in addition to the commitment to the object; and that if the parts of an object are ‘ontologically innocent’, then sums cannot fail to be innocent either

The idea that two objects can coincide—by sharing all their proper parts, or matter—yet be non-identical, results in the “Problem of Coincident Objects”: in what relation do objects stand if they are not identical but share all their proper parts? One solution is to introduce material constitution. In this paper, I argue that this is ad hoc since, first, this solution cannot be generalized to solve similar problems, and, second, there are pseudo cases of coincidence that should not trigger the introduction of material constitution and these cannot be distinguished in any principled way from the allegedly real cases of coincidence.

Some philosophers say that a whole is “nothing over and above” its parts. Most also take general extensilonal mereology to be treating wholes as “nothing over and above” their parts. It is not always clear, however, what exactly is meant by the phrase “nothing over and above.” Nor is it obvious why the phrase is associated with mereology, and what purpose it serves there. In the words of Peter Van Inwagen : “This slippery phrase has had a lot of employment in philosophy, but what it means is never explained by its employers.” This paper sheds light on the various senses in which one might hold that a whole is “nothing over and above” its parts, and on how these senses are related both to each other and to mereology.

In a recent article, David distinguishes between two interpretations of Tarski’s work on truth. The standard interpretation has it that Tarski gave us a definition of truth in-L within the meta-language; the non-standard interpretation, that Tarski did not give us a definition of true sentence in L, but rather a definition of truth, and Tarski does so for L within the metalanguage. The difference is crucial: for on the standard view, there are different concepts of truth, while in the alternative interpretation there is just one concept. In this paper we will have a brief look at the distinction between these two interpretations and at the arguments David gives for each view. We will evaluate one of David’s arguments for the alternative view by looking at Tarski’s ‘On the concept of truth in formalized languages’, and his use of the term ‘extension’ therein, which, we shall find, yields no conclusive evidence for either position. Then we will look at how Tarski treats ‘satisfaction’, an essential concept for his definition of ‘true sentence’. It will be argued that, in light of how Tarski talks about ‘satisfaction’ in Sect. 4 of ‘CTF’ and his claims in the Postscript, the alternative view is more likely than the standard one.

Core principles of mereology have been questioned by appealing to time travel scenarios. This paper questions the methodology of employing time travel scenarios to argue against mereology. We show some time travel scenarios are structurally equivalent to more standard ones not involving time travel; and that the three main theories about persistence through time can each solve both the time travel scenario as well as the structurally similar classical scenario. Time travel scenarios that are not similar to more standard arguments are instead problematic because they are open to different, incompatible interpretations. We conclude that compared to the classical arguments against mereological principles, time travel scenarios do not add anything new.

Standard principles of mereology, such as the transitivity and asymmetry of proper parthood, have been questioned, using various multi-location scenarios. The most famous of these is Borges’s Aleph, although the literature is rife with other examples that allegedly show that some mereological principle is at odds with some form of multi-location. However, the scenarios only support this conclusion given various bridge principles that link location to parthood. I argue that the bridge principles that guarantee the desired conclusion are controversial partly because they give the wrong result in other situations, in particular cases of co-location. Moreover, less controversial bridge principles do not provide an incompatibility result between standard mereological principles and multi-location. Hence, multi-location does not threaten any standard mereological principles.

One of the more persistent debates in mereology is whether distinct wholes can have the same parts. Extensional mereologists hold that if there is no part that makes the difference, then there is nothing to distinguish the wholes, so sameness of parts implies identity. Non-extensionalists, however, do think there are cases where distinct wholes share all their parts. This paper argues that the kind of argument non-extensionalists employ can also be levelled against a widely accepted extensionality principle of plural logic. Non-extensionalists thus face a dilemma: either give up the argument for non-extensional mereology, or deny both the extensionality principle of mereology and the analogous principle for plural logic.

A.J. Cotnoir has argued that we should distinguish between two notions of proper parthood: outstripped part and non-identical part. Outstripped parthood is an asymmetric relation, but non-identical parthood is not. We argue, first, that the intuitions Cotnoir uses to motivate these notions do not always give the right verdict; and, second, that systematic reasons for distinguishing these two notions of parthood have further counter-intuitive consequences. This means the distinction between two notions of proper parthood currently lacks adequate motivation.

Classical mereology is a particularly strong theory about the part–whole relation. Not only does it ensure that any collection of entities composes a whole, or ‘fusion’, it also states that this object is unique: no two entities have the same parts. Recently, Claudio Calosi (dialectica 68(1):121–139, 2014) has argued that this extensional aspect makes classical mereology incompatible with multilocated entities. Calosi’s argument is arguably the most precise one from a whole battery of arguments to the effect that some mereological principle is at odds with multilocation. Still, I show that Calosi’s arguments fail and that classical mereology is a safe space for multilocation. Moreover, I argue that the question of extensionality is orthogonal to the question of multilocation.

Classical mereology seems unable to characterise the identity conditions of word types. For example, the same letter types ordered differently result in different word types; but mereological fusions of the same letters are identical, regardless of the order of the letters. We show, however, that by combining classical mereology with plural logic one can give a definition of word types that satisfies the identity criteria of word types. This means that it is not necessary to abandon classical mereology in order to give an analysis of the mereological structure of word types.

Classical mereology is a particularly strong theory about the part–whole relation. Not only does it ensure that any collection of entities composes a whole, or ‘fusion’, it also states that this object is unique: no two entities have the same parts. Recently, Claudio Calosi (dialectica 68(1):121–139, 2014) has argued that this extensional aspect makes classical mereology incompatible with multilocated entities. Calosi’s argument is arguably the most precise one from a whole battery of arguments to the effect that some mereological principle is at odds with multilocation. Still, I show that Calosi’s arguments fail and that classical mereology is a safe space for multilocation. Moreover, I argue that the question of extensionality is orthogonal to the question of multilocation.

When a theory is confronted with a problem such as a paradox, an empirical anomaly, or a vicious regress, one may change part of the theory to solve that problem. Sometimes the proposed solution is considered ad hoc. This paper gives a new definition of ‘ad hoc solution’ as used in both philosophy and science. I argue that a solution is ad hoc if it fails to live up to the explanatory requirements of a theory because the solution is not backed by an explanation or because it does not diagnose the problem. Ad hoc solutions are thus magical: they solve a problem without providing insight. This definition helps to explain both why ad hoc solutions are bad and why there may be disagreement about cases.