Going by its Wikipedia page, materialism has been largely discredited due to advances in physics as it cannot explain phenomena such as gravity which apparently exist without the connivance of matter. Considering some of the dates involved in the history of materialism—the earliest in the wiki being ~6th century BCE—how did materialists historically fit magnetism, a known phenomenon at the time, into their model?
According to John Burtnet, Thales believed that:
- The earth floats on the water.
- Water is the material cause of all things.
- All things are full of gods. The magnet is alive; for it has the power of moving iron.
Aristotle said, in De Anima:
Certain thinkers say that soul is intermingled in the whole universe, and that it is perhaps for that reason that Thales came to the opinion that all things are full of gods.
Thales, too, to judge from what is recorded about him, seems to have held soul to be a motive force, since he said that the magnet has a soul in it because it moves the iron.
In other cases, magnetism was regarded as "divine attraction" -- in other words, magic. It's also noteworthy to say that even though materialists believed that all things are made up of material stuff -- be it water, earth, fire, etc -- this did not mean that souls could not exist (see Epicurus, for example). Empedocles, another materialist, actually believed in the transmigration of souls.
Here's a great paper that discusses magnetism and electricity in ancient Greece. Awesome question, +1.