ABSTRACT
By knowledge I mean structured knowledge, not collections of isolated facts such as form the content of many television quiz shows. We already know that the latter are of low adaptability, as is well illustrated by the following example from Rees. 1 Craft apprentices had learnt at school that the area of a circle is given by the formula pr 2 , where r is its radius. They needed to calculate the area of cross-section of a given piece of wire, so they began by measuring its thickness. This gives the diameter of the circular cross-section, not the radius. No problem, you may think: they know that the radius of a circle is half the length of a diameter, so if they know the diameter they can easily find the radius and apply the formula. But hard though it is to believe, many of these apprentices could not do this. Though they had the necessary facts, they were not able to combine them to make a plan for dealing with the requirements of this new situation.
