The fallacy of composition occurs when one attempts to make a claim about the whole based on some property of its parts. Occasionally, this style of argumentation produces valid results:
Every part of the machine is green, therefore the machine itself is green.
But watch out:
Every part of the machine weighs one pound, therefore the machine itself weighs one pound.
Now consider this from Dr. Vallicella's recent post:
Maybe it goes like this. I have a head full of homunculi. These little men and women, working together, ascribe intentionality to me. But each homunculus has its intentionality ascribed to it by other, stupider, homunculi which are constituents of it. The stupider homunculi, in turn, are composed of even stupider ones, and so on until we get to the level of individual neurons which, as Pollack says, "aren't 'about' anything." The base level homuncuili are so stupid that one could say that they don't even rise to the level of being either stupid or intelligent.
Does this avoid the dilemma of having to choose between a vicious infinite regress and a vicious circle? What Dennett is proposing is a finite regress that terminates with something naturalistically acceptable, namely entities that lack intrinsic or original intentionality.
Admittedly, this proposal gets rid of the infinity of the regress, but not its viciousness: we still have no explanation of intentionality. Consider the base-level homunculi. They are so primitive as to lack all intentionality. How then can they ascribe intentionality to their colleagues one level up? (italics added)
I may be wrong, but this strikes me as an example of the fallacy of composition. Consider the following:
Cells are all stupid, therefore a composite cellular entity would also be stupid.
False, right? The fact is that people-- including the smart ones-- are composed of cells.
The building blocks of mind are themselves mindless. Therefore no composite of these mindless building blocks can result in mind.
While the jury is still out on whether substance dualism or some form of materialism is closer to the truth, I think it's safe to say the above italicized claim is likely false.