This chapter attempts to illuminate the dynamic stability of the organism and the robustness of its developmental pathway by considering the biology of cancer. Healthy development and stable functioning of a multicellular organism require an exquisitely regulated balance between processes of cell division, differentiation, and death (apoptosis). Cancer involves a disruption of this balance, which results in unregulated cell proliferation. The thesis defended in this chapter is that the coupling between proliferation and differentiation, whether normal or pathological (as in cancer), is best understood within a process-ontological framework. This framework emphasizes the interactions and mutual stabilizations between processes at different levels and this, in turn, explains the difficulty in allocating the neoplastic process to any particular level (genetic, epigenetic, cellular, or histological). Understanding these interactions is likely to be a precondition of a proper understanding of how these mutual regulations are disrupted in the processes we call cancerous.