There's another way of looking at the educational process involving dependencies. It is widely understood that learned concepts often have prerequisites. Knowledge often depends on previous knowledge. For example, understanding written sentences depends on an understanding of the words involved which in turn depends on a knowledge of the alphabet. Knowledge can thus be pictured as an edifice in which higher structures depend on lower ones.
However, in large construction projects, scaffolding is often used. Scaffolding supports the structure while it is under construction and is then eventually removed. It seems obvious that some learning materials play the role of scaffolding in the construction of knowledge. For example, ABC books are on the bookshelves of toddlers, but not the bookshelves of adults. Adults don't need them any more.
Some concepts too get discarded during the learning process. I can clearly remember as a child thinking of my reputation as a nebulous fog that surrounded me which other minds interacted directly with. That might have been a useful concept which helped me to avoid making mistakes at the time, but I now know that it was a largely mistaken idea. Santa Claus, the tooth fairy, God, heaven and hell are all ideas which are regularly taught to children and are later discarded as the child grows up.
Educational scaffolding has been well studied by developmental psychologists since the 1950s. This Wikipedia article has more details of that.
Scaffolding, I would argue, is an abstract engineering concept which is useful for building all kinds of structures, from buildings to scientific theories. We could have a scaffolding theory that abstracts away substrate specific details and is applicable in a wide variety of domains. It could cover issues such as the following:
- What type of scaffolding to use;
- How much scaffolding to use;
- When to add scaffolding;
- When to remove scaffolding;
- How to attach the scaffolding;
Scaffolding is also a useful concept in biology. One application domain is ontogeny. The placenta is an example of developmental scaffolding that is discarded after being used. Removal of scaffolding sometimes leaves scars - and in this case, the belly button is an example of a scar marking a scaffolding attachment point that persists throughout life. A corresponding example from cultural evolution involves baking a cake. A cake tin acts as scaffolding for the cake. As with the belly button the tin leaves a scar that persists throughout the life of the cake. Another application domain is evolutionary theory. Evolution critic Michael Behe once defined the concept of "irreducible complexity" in his book Darwin's Black Box as follows:
A single system which is composed of several interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning.
He went on to argue that "irreducibly complex" systems cannot evolve by a process involving small changes. However, of course such systems can evolve by using small changes - if they employ scaffolding. An stone arch depends on every stone: remove one stone and the arch collapses. However an arch can still be built by a gradual process of adding and removing stones. The key to construction is to use a mound of stones under the arch that supports it while it is being created. The mound is removed once the arch is complete.
For scaffolding in evolution, a lot of the engineering concerns listed above don't apply. Instead what would be useful are theories about how to identify details about missing scaffolding after it has been removed.