There are at least three vaguely atomistic principles that have come up in the literature, two explicitly and one implicitly. First, standard atomism is the claim that everything is composed of atoms, and is very often how atomism is characterized in the literature. Second, superatomism is the claim that parthood is well-founded, which implies that every proper parthood chain terminates, and has been discussed as a stronger alternative to standard atomism. Third, there is a principle that lies between these two (...) theses in terms of its relative strength: strong atomism, the claim that every maximal proper parthood chain terminates. Although strong atomism is equivalent to superatomism in classical extensional mereology, it is strictly weaker than it in strictly weaker systems in which parthood is a partial order. And it is strictly stronger than standard atomism in classical extensional mereology and, given the axiom of choice, in such strictly weaker systems as well. Though strong atomism has not, to my knowledge, been explicitly identified, Shiver appears to have it in mind, though it is unclear whether he recognizes that it is not equivalent to standard atomism in each of the mereologies he considers. I prove these logical relationships which hold amongst these three atomistic principles, and argue that, whether one adopts classical extensional mereology or a system strictly weaker than it in which parthood is a partial order, standard atomism is a more defensible addition to one’s mereology than either of the other two principles, and it should be regarded as the best formulation of the atomistic thesis. (shrink)

According to the thesis known as ‘Composition as Identity’ (‘CAI’), every entity is identical to the parts it fuses. Many authors in the literature acknowledge that, in spite of its controversial character, one attractive virtue of CAI is its apparent ability to give a straightforward account of the innocence of mereology. In this paper I will present a simple argument according to which CAI entails that no composite entity can be said to be ontologically innocent in the relevant sense. After (...) having shown that said argument is independent from the problems surrounding the infamous ‘Collapse Principle’, I will conclude that CAI-theorists should endorse a suitably ‘restricted’ version of CAI. In the final part of the paper I will then argue that the best restricted version of CAI is the theory according to which every composite entity is identical to the plurality of its atomic parts. (shrink)

This paper investigates two intuitionistic mereological systems based on Tarski’s axiomatisation of general mereology. These systems use two intuitionistically non-equivalent formalisations of the notion of fusion. I study extensionality and supplementation properties as well as some variants of these systems, and defend parthood as a suitable primitive notion for intuitionistic mereology if working with Tarski’s axiomatisation. Furthermore, I arrive at an equi-interpretability result for one of the atomistic variants with intuitionistic plural logic. I discuss to what extent these results support (...) the philosophical pertinence of the mereological systems under investigation as intuitionistic theories of parthood, thereby reacting to a conceptual challenge that we are confronted with when engaging in intuitionistic mereology. (shrink)

Mereological atomism is the thesis that everything is ultimately composed of atomic parts, i.e., parts without proper parts. Typically, this thesis is characterized by an axiom stating that everything has atomic parts. The present paper argues that the success of this standard characterization depends on how the notions of sum and composition are defined. In particular, we put forward a novel definition of mereological sum that: (i) is not equivalent to existing definitions in the literature, if no strong decomposition principle (...) is assumed; (ii) can be used to argue that the standard characterization of atomism fails, because having atomic parts is not sufficient to be a sum of atoms; and (iii) provides a purely mereological distinction between structured and unstructured wholes, contributing to the ongoing debate on this crucial topic. (shrink)