Full Idea
As long as your homunculi are more stupid and ignorant than the intelligent agent they compose, the nesting of homunculi within homunculi can be finite, bottoming out, eventually, with agents so unimpressive they can be replaced by machines.
Clarification
'Homunculi' are little men
Gist of Idea
Intelligent agents are composed of nested homunculi, of decreasing intelligence, ending in machines
Source
Daniel C. Dennett (Sweet Dreams [2005], Ch.6)
Book Reference
Dennett,Daniel C.: 'Sweet Dreams' [MIT 2005], p.137
A Reaction
[Dennett first proposed this in 'Brainstorms' 1978]. This view was developed well by Lycan. I rate it as one of the most illuminating ideas in the modern philosophy of mind. All complex systems (like aeroplanes) have this structure.