In functional analysis, one attempts to explain a function of interest by decomposing into an organized system of subfunctions (Cummins, 1981). This approach can be iteratively applied to explain any of the subfunctions that appear at any stage of the functional analysis. This leads, in theory, to an infinite proliferation of functional terms which would prevent the functional analysis from being explanatory (Ryle, 1949). This problem with functional analysis has been called Ryle’s regress.
To make a functional analysis explanatory, Ryle’s regress must be stopped. This means that there must be some stage in a functional analysis at which a subfunction can be explained without further decomposing it into sub-subfunctions. In Cummins’ (1981) functional analysis, this is accomplished by subsubsumption. A function is said to be subsumed when one can explain how it works by appealing to the causal laws governing some mechanism that is capable of producing the function. For example, one can subsume the function in color vision that “detects medium wavelength light” by appealing to the physical changes that occur in the particular photopigment molecules contained in retinal cone cells that are most sensitive to light in the green range of the color spectrum.
If one must subsume functions to make a functional analysis explanatory, then this suggests that as one iteratively decomposes functions into subfunctions, the subfunctions that result must be simpler. This approach has also been described by Dennett (1978) as “discharging intelligence” or “discharging homunculi”. Dennett’s approach requires that subcomponents become less intelligent as an analysis becomes more fine-grained. At some point, the degree of intelligence becomes so small that the function can be replaced by a simple physical device (e.g. a neuron that in essence answers yes or no to a very simple question).
- Cummins, R. (1983). The Nature Of Psychological Explanation. Cambridge, MA.: MIT Press.
- Dennett, D. (1978). Brainstorms. Cambridge, MA: MIT Press.
- Ryle, G. (1949). The Concept Of Mind. London: Hutchinson & Company.
(Added January 2010)