The thesis is about Multiple Realization. Multiple realization is roughly the idea of a higher level property being multiply realized by different lower level physical properties. Philosophers usually argue that if a property is multiply realized, it is not reducible to its realizers. Mobilized as such, multiple realization plays a central role in what is usually called Non-Reductive Physicalism. Despite its popularity, and beyond the hunches and intuitions that back the concept, seldom do philosophers consider the nature of multiple realization. (...) The central aim of the thesis is to tackle the somewhat overlooked question: “what is multiple realization?” The rationale is that to find out what philosophical tasks multiple realization can accomplish, we have to know what multiple realization is. The thesis proceeds as follow: In chapter 2, I’ll argue for a methodology for the entire project in answering the question. I’ll argue that there are four desiderata we want from any account of multiple realization, namely, Multiplicity, Naturalness, Physical Realization, and Anti-Reductionism. We should look for an account of multiple realization that could respect the four desiderata in a philosophically satisfactory way. In chapter 3, I’ll look at the alleged origin of multiple realization, Jerry Fodor’s. I’ll reconstruct Fodor’s account of multiple realization. I’ll argue that the major bug of Fodor’s account is his failure in respecting Physical Realization. In chapter 4, I’ll examine Jaegwon Kim’s important critique of Fodor. I’ll argue that Kim’s criticism can be reconstructed as an account of multiple realization that intentionally violates Naturalness. In chapter 5, I’ll look at what I call the Causal Power Subset View of multiple realization as suggested by some philosophers around the turn of the 21st century. I’ll reconstruct an account of multiple realization from their works and argue that their account faces difficulties in reconciling Physical and Anti-Reductionism. I’ll further argue that their account nudges us toward a representational reading of Anti-Reductionism, according to which our seeming commitment to the higher level realized property is, in fact, a partial representation of a complex physical state. In chapter 6, I develop the aforementioned suggestion into a fuller picture. I’ll sketch a representational account of multiple realization and elucidate its plausibility. One result of the thesis is that the desiderata motivating a theory of multiple realization are in tight tension. One has to choose among them. My approach is no exception. I choose to give up Anti-Reductionism and Naturalness, but, as a remedy, I attempt to explain and make sense of the motivations and intuitions backing these two desiderata, arriving at a picture that I am comfortable with, after traveling the long journey. (shrink)