The
idea that
everything is made up of many
smaller
replicas of itself, for example a
vacuum cleaner consists of smaller
vacuum cleaners, which are of course made up of even smaller ones,
ad infinitum.
A variation on this theory states that the smaller-thing recursion stops after one level, that is, a vacuum cleaner is made up of smaller vacuum cleaners that actually do the vacuuming.
A compromise between these two forks stipulates that there are indeed many levels of recursion, but after a certain point, it's all turtles. We call this the "Turtle Point." This is clearly the silliest of the three theories, and is thus the dominant one.