This book chapter provides revitalizing thoughts on the meaning of theory, theorizing, and philosophizing in the field of Information Systems (IS). More specifically, the chapter scrutinizes and explicates central definitions of theory, theorizing, philosophy, and philosophizing, in the context of developing theoretical implications as a part of a larger theory development project. Additionally, the chapter introduces the concept of kernel philosophiesand conceptualizes different spaces for theory development projects in IS. Finally, the chapter ends with concluding remarks on philosophy and philosophizing as supportive medium for the theorizing process in IS.