We often say that things are parts of others things. My hand is a part of me. New York State is a part of the U.S. The goalie is a part of the team. The letter 'a' is a part of the word 'and'. We also say that some objects are composed of others. My body is composed of my foot, my mouth, and so on; the U.S. is composed of 50 states and some territories. The team is composed of players, coaches, and staff. The word 'and' is composed of three letters: 'a', 'n' and 'd'. The study of relations like parthood and composition is known as mereology. The central task of mereology is to understand when and how objects are built from other objects. Agreement in mereology, however, does not seem forthcoming. And this isn't just your run-of-the-mill philosophical stubbornness. Case in point: some mereologists think of parthood as a logical notion akin to conjunction; others as a physical notion akin to having mass. Moreover, the former often accuse the latter of being conceptually confused: one mereologist's conceptual truth turns out to be another's contingent falsehood. Thus, mereological disputes have become the poster child for metaphysical anti-realism. Anti-realism or not, though, it is hard to shake the feeling that there is something fundamentally misguided about mereological inquiry. Accordingly, this dissertation engages in what may as well be called metamereology. It aims to answer questions like: what are we doing when we do mereology? How can we make progress on notoriously stubborn mereological disputes? What, if anything, turns on the resolution of such disputes? The first half constitutes the negative thrust of the project. There, I aim to identify and overcome obstacles to productive mereological discussion. In doing so, I hope to clarify exactly what is at stake in traditional mereological debates. The second half constitutes the positive thrust. In particular, I offer a proof-of-concept of how I believe mereological inquiry should proceed. The approach I suggest is a fairly holistic one that places the theoretical work that mereology can do in our best theories front and center. In particular, chapters five and six explore the role of mereology from the perspective of a generally Humean approach to metaphysics.