In this special issue devoted to speaking across communication subfields, we introduce a domain general explanatory framework that integrates biological explanation with communication science and organizes our field around a shared explanatory empirical model. Specifically, we draw on David Marr's classical framework, which subdivides the explanation of human behavior into three levels: computation (why), algorithm (what), and implementation (how). Prior theorizing and research in communication has primarily addressed Marr's computational level (why), but has less frequently investigated algorithmic (what) or implementation (how all communication phenomena emerge from and rely on biological processes) explanations. Here, we introduce Marr's framework and apply it to three research domains in communication science-audience research, persuasion, and social comparisons-to demonstrate what a unifying framework for explaining communication across the levels of why, what, and how can look like, and how Marr's framework speaks to and receives input from all subfields of communication inquiry.