 Arguments of the above kind — that is, arguments leading to definite conclusions on the basis of an initial symmetry of the situation plus PSR — have been used in science since antiquity (as Anaximander’s argument testifies). The form they most frequently take is the following: a situation with a certain symmetry evolves in such a way that, in the absence of an asymmetric cause, the initial symmetry is preserved. In other words, a breaking of the initial symmetry cannot happen without a reason, or an asymmetry cannot originate spontaneously. Van Fraassen (1989) devotes a chapter to considering the way these kinds of symmetry arguments can be used in general problem-solving.