 Inherent in the philosophy of logical empiricism, broadly construed, is a strong opposition to traditional metaphysics. Not surprisingly, many of the logical empiricists were guided by Humean empiricist principles. Even some concepts of scientific language were suspected to be metaphysical in nature. Wittgenstein (1922: 5.136) held that belief in a general law of causality is superstition. He also denied that laws of nature could explain natural phenomena (6.371n). Frank (1932: Ch. V, IX) pointed out several difficulties in giving a precise formulation of a general law of causality. Russell (1913) argued that the notion of cause is beset with confusion, and should better be excluded from philosophical vocabulary.