In this paper, I put forward a theory about the modes and dimensions of being. In the first section, I define existence through coexistence, understood as the codetermination of certain things and processes via other things and processes. In the second section, I differentiate between modes and dimensions of being. In the third section, I argue that the modes of existing are the different ways in which coexistence and codetermination take place and discuss two types of modes ("fundamental" and "categorial"), (...) to subsequently present a classification thereof. In the fourth section, I posit a theory about the dimensions of any existing thing or process, arguing for the existence of two types of dimensions: configurational and processual. (shrink)