Diagnosing an illness, finding a fault in an electrical circuit, responding to developments in the marketplace or in relationships between people, for instance, can all benefit from understanding. It can have the potential to free a learner from the limitations of memorized knowledge. Someone whose responses are tied inflexibly to particular

circumstances is at a loss when those circumstances change. Isaac Newton, in a letter to Nathaniel Hawes in 1694 explained that any ‘Mechanick’ may be able to do what he has been shown but if things go wrong, he is at a loss how to proceed unless he also understands it (Westfall, 1980; Christianson, 1984). As Halford (1993) put it, understanding can confer a certain cognitive autonomy on its owner. It has the potential to enable effective, independent interaction with the world. It can enable people to think for themselves and make reasoned choices (Meijer, 1991). In effect, it frees people from inflexible, non-adaptive behaviours and it includes a capacity to explain, justify, think critically and, in certain circumstances, predict and control events (Johnson-Laird, 1985; Petroski, 1993). For instance, knowing the causes of condensation can enable us to explain its occurrence and prevent it in a particular room. Understanding enables its owner to evaluate the arguments of others and to give them due weight. For example, a politician attempting to persuade us of the merits of a course of action might draw an analogy with an event in the past. Understanding such events can help evaluate the attempted justification. Creative thought, understanding and flexible behaviour are closely related.