Aristotelian substance theory tells us that substances have structures (read: forms) as proper parts. This claim has recently been defended by Kathrin Koslicki who dubbed it the ‘Neo-Aristotelian Thesis.’ Strangely, Aristotelianism has not yet been universally embraced by philosophers – partly because some of its claims, such as the Neo-Aristotelian Thesis – are viewed by some as counterintuitive at best. In this paper, I argue for Aristotelianism by showing its philosophical usefulness: specifically, I put it to use in saving the metaphysical doctrine of endurantism and some central mereological doctrines (such as Transitivity) from recent attacks. This utility gives us reason to endorse Aristotelianism. Along the way, I defend Koslicki's argument for the Neo-Aristotelian Thesis from a recent criticism, thus helping provide still more reason to endorse Aristotelianism: namely, Koslicki's vindicated argument.