A prominent and significant challenge to reductionism stems from the fact that higher level biological structures and processes can be realized by different kinds of molecular processes, so that many molecular kinds can correspond to one higher level kind (Section 4.2).
Elliott Sober (1999) extends this line of argument: an explanation in terms of higher level kinds can be more unified or general by encompassing heterogeneous lower level kinds, but this same heterogeneity exhibits important differences in scientifically interesting properties.
Apart from the one-many relation between molecular and higher level kinds, Hull (1972, 1974 , 1976 also points to the existence of a many-one relation as a challenge for reductionism.
He argues that it is not that the complexities of any reduction (due to the many-one relations between molecular and higher level kinds) exceed our cognitive capacities.
Some critiques of (epistemic) reductionism emphasize that the effects of molecular processes strongly depend on the context in which they occur, so that one molecular kind can correspond to many higher level kinds (Section 4.1).
Principles of classical genetics (e.g., segregation) are explained by cellular processes (e.g., the behavior of chromosomes in meiosis) because the higher level kinds picked out by cytology are causally relevant.
This sense of one many relations between molecular and higher level kinds does not necessarily preclude some types of reduction, but explanations in molecular biology must to be sensitive to the associated epistemic issues.
At a higher level, the same kind of "commander's intent" from the White House would help clarify, for instance, how a U.S. missile strike in Syria fits into an overall strategy of bringing down the regime of President Bashar Assad or ending the Syrian war.
A new cohort of younger older adults (baby boomers) would probably present a higher level of acceptance of this kind of robotic device.
Having stated this opinion, I would now like to explain at a higher level why incompleteness of the kind seen here is not a problem for the process of science.
Hull's point is that the same higher level phenomenon (e.g., a Mendelian trait such as coat color) can be produced by several different molecular mechanisms, or that a higher level phenomenon is realized by different kinds of molecular configurations (multiple realization).
