Unbalanced

Back in the Europe of the Middle Ages there existed a curiously schizophrenic attitude to the question of whether the Earth was at the center of the universe. The doctrine of the established Catholic Church decreed that it was. The practical evidence suggested that it wasn't and the orthodox scientific theory endeavored to fit the evidence to the theory, at the expense of commonsense and logic.

Today there exists a similarly curious attitude to the question of whether or not economics is governed by people making rational decisions in consistent ways. The doctrine of the established economic theory says that it is. The practical evidence suggest that it isn't. And the orthodox economic theories endeavor to fit the evidence to the theory, at the expense of commonsense and logic.

Wandering Greeks

The word planet comes from the Greek for “wanderer”, and that name arises from the Ancient Greek observation of wandering stars that confounded theories of an Earth-centric universe. If the Earth is stationary and the universe revolves around it then the stars should orbit us in a calm and predictable manner. What they shouldn't do is suddenly stop and then go into reverse before executing a reverse somersault and double pike. But they do.

Of course we now know that the other planets in the Solar System aren't orbiting us, and from our perspective this means that sometimes they will perform odd manoeuvres: they will wander, and this, you might think, rather buggers up the idea that we're at the center of everything. But never, ever underestimate the ingenuity of a clever person with a pet theory that they're committed to. 

Circular Reasoning

There was a second idea that needed to be incorporated in the model of the universe, the idea of circular motion. This seems to have arisen from Aristotle's belief that the circle was the perfect form, and led to the assumption that orbits were based on uniform circular motion. This was to cause a deal of trouble later on, but we'll come to that eventually.