 So well into the second decade of the new millennium, a renewed critical interest in multiple realizability continued to generate new discussions and arguments on both sides, pro and can. The assumption, unfortunately still too common in philosophy of mind, that multiple realizability “seals the deal” against reductive physicalism and mind-brain identity theory, was mistaken back in the 1970s and 1980s (see  §2  above), and grew even more discredited by the full scope of published literature on the topic that has followed since. But equally unfortunately, the literature on multiple realizability had taken off in numerous varied directions, and following out any one of these leads one quickly into detailed complicated and technical discussions, in both philosophy and science, and often at quite a distance from those who follow out arguments in other directions. And the fate of one of the most influential arguments in late-twentieth century Anglo-American philosophy hangs in the balance, in all of these debates. By the second decade of the new millennium, concerns about multiple realizability arguments had grown beyond their philosophy of mind origins, into more general questions about relationships obtaining between sciences addressing higher and lower levels of the world’s organization. What the issue needed now was a single work that captured both the full scope of writings on this topic, and with a focus unifying all of these diverging literatures. Fortunately, such a work appeared, and it and its critical reception is the focus on the next section.