In this commentary, I consider each of the papers in this special issue in regard to their contribution to a debate on the nature of learning in physical education (PE). I also discuss how we might take this aspiration further by moving beyond a "mere" debate over learning theories to a knowledge building process in which knowledge claims are "tested" against their compatibility (or non-compatibility) with other "knowings". In this regard, I introduce the idea of "vertical integration" or "compatibility" as a consideration for building a more mature field of study of learning in PE.