Q: How does one reconcile Levels of Abstraction (LoA) and Emergentism if one “level” cannot in its entirety (ontologically) be reduced to its lower, more fundamental level, e.g., biology to chemistry, chemistry to physics? 

Per Mill and Broad, there are novel properties introduced at each level of increasing organizational complexity of matter, that is, ”primitive high-level causal interactions that are additional to those of the more fundamental levels.” 

Or, per Alexander, do these “additional causal interactions represent macroscopic patterns [already] running through those very microscopic interactions [where] [e]mergent qualities are something truly new under the sun, but the world’s fundamental dynamics remain unchanged”? 

Simply put, can one still speak of levels of abstraction as explanation if levels remain incommensurable due to novel properties specific to each level?

Note: Couldn’t the orthodox Marxist who aims to protect class antagonism as the driving force of history turn to emergentism to fend off some challenges (i.e., via levels of abstraction) to those dialectics? Yes, yes, to protect Marxist reductionism? [Fodor addresses this?]