Goethe quote

Every school of thought is like a man who has talked to himself for a hundred years and is delighted with his own mind, however stupid it may be.
(J.W. Goethe, 1817, Principles of Natural Science)

From the Schools of Thought page of the History of Economic Thought site. I think that site is a very good starting point for serious economic study.

update (25th December): Here is a counter balancing quote, from the HET introduction page, also from Goethe

Somebody says: "Of no school I am part,
Never to living master lost my heart,
Nor any more can I be said
To have learned anything from the dead."
That statement - subject to appeal -
Means "I'm a self-made imbecile."
(J.W. Goethe, Den Originalen, 1812)