 Lakatos objects that although there is something to be said for Popper’s criterion, it is far too restrictive, since it would rule out too much of everyday scientific practice (not to mention the value-judgments of the scientific elite) as unscientific and irrational. For scientists often persist—and, it seems, rationally persist—with theories, such as Newtonian celestial mechanics that by Popper’s standards they ought to have rejected as “refuted”, that is theories that (in conjunction with other assumptions) have led to falsified predictions. A key example for Lakatos is the “Precession of Mercury” that is, the anomalous behaviour of the perihelion of Mercury, which shifts around the Sun in a way that it ought not to do if Newton’s mechanics were correct and there were no other sizable body influencing its orbit. The problem is that there seems to be no such body. The difficulty was well known for decades but it did not cause astronomers to collectively give up on Newton until Einstein’s theory came along. Lakatos thought that the astronomers were right not to abandon Newton even though Newton eventually turned out to be wrong and Einstein turned out to be right.