 His work on causation led Flichman (1990, 1995) to discuss the concept of scientific law: according to him, the distinction between laws of nature and accidental uniformities depends on the role they play in a scientific theory; moreover “hard” and “soft” accidental uniformities must be carefully distinguished because the latter are frequently confused with laws of nature. Pablo Lorenzano (1998, 2007) also reflects upon the concept of law of nature in relation to the existence of biological laws.