Friday, January 25, 2008

Reductionism vs. Downward Causation

The article Downward Causation contains this quote describing downward causation:

all processes at the lower level of a hierarchy are restrained by and act in conformity to the laws of the higher level


The counterpart of downward causation is reductionism. Quoting from the same article:

Reductionism can be defined as the belief that the behavior of a whole or system is completely determined by the behavior of the parts, elements or subsystems. In other words, if you know the laws governing the behavior of the parts, you should be able to deduce the laws governing the behavior of the whole.


Note the philosophical outlook underlying reductionism. Knowledge about the parts leads to deductions about laws governing the whole. That's the paradigm through which investigations about the origin of life take place. Laws governing chemical reactions of organic compounds yield information from which laws governing cells can be deduced. But if such laws cannot be deduced then what? The "then what" may explain the spinning wheel results accruing from decades of OOL research. Our understanding of the chemical properties of cellular biochemicals provides no insight as to how reactions, involving such chemicals, leads to the formation of cells. Reductionist approaches have not led to progress. More from the same article:

Systems theory has always taken an anti-reductionist stance, noting that the whole is more than the sum of the parts. In other words, the whole has "emergent properties" which cannot be reduced to properties of the parts. Since emergence is a rather slippery concept, which has been defined in many different ways, most of which are highly ambiguous or fuzzy, I prefer to express this idea with the more precise concept of downward causation.


Cells indeed do have properties that are not reducible to the chemical properties of their constituent biochemicals. For example, cellular DNA is able to store genetic information that, when expressed, enables the synthesis of RNA, proteins and cellular structures consisting of proteins. This is possible because of the ordering of nucleotides according to patterns that conform to what are referred to as genetic codes. Yet the codon sequences within DNA do not have to be functionally ordered to retain their chemical properties. Chemical properties of DNA are indifferent to the unique sequencing needed to confer cellular function. DNA is DNA whether biologically functional or otherwise. Ribosome function is not explained by specifically referencing the properties of its individual proteins and RNA. It must be viewed holistically.

Do all systems exhibiting downward causation owe their origin to causes traceable to the properties of their constituent parts? Or does a causal flow downward better account for the origin of systems as well? Michael Behe's irreducible complexity can be viewed as an indicator of downward causality. Downward causality is exhibited in intelligently designed systems. The flow begins with an intelligent plan which, when put into effect, results in an arrangement of parts that make function possible. Technology is created this way.

Reductionists argue that the brain itself (intelligence) lies at the end of a causality trail that commenced with biological systems emerging from simpler biochemical reactions. That however is a belief not sustained by empirical results. When we follow existing causal trails we find no logical barrier to investigating a directional flow downward. Indeed excluding it a priori is a philosophical choice; not an empirical necessity.

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