Philosophical materialism is not a recent fad and it is not a solid block: it is as old as philosophy and it has gone through six quite different stages. The first was ancient materialism, centered around Greek and Indian atomism. The second was the revival of the first during the 17th century. The third was 18th century ma­ terialism, partly derived from one side of Descartes' ambiguous legacy. The fourth was the mid-19th century "scientific" material­ ism, which flourished mainly in Germany and England, and was tied to the upsurge of chemistry and biology. The fifth was dialec­ tical and historical materialism, which accompanied the consolida­ tion of the socialist ideology. And the sixth or current stage, evolved mainly by Australian and American philosophers, is aca­ demic and nonpartisan but otherwise very heterogeneous. Ancient materialism was thoroughly mechanistic.