"Three categories of people confronted or confront situations that are in many ways closely analogous. ...[T]he original inventor of a theorem or techinique... applies to the solution of his problems the mathematical tools he has inherited but slowly or quickly intuits more powerful ways... [T]he historian... seeks, hampered by his... hindsight, to retrace via texts and artifacts the thought processes of the inventor. ...[T]he student, for whom a given problem is as new as ever ...People in all three categories share... an inability to grasp the full implications of their own accomplishments. Both the historian and the student can gain understanding from the example of the inventor."