Murphy caused the law, but he didn't formulate the law. According to Spark1, who investigated the origins of Murphy's Law, it was first launched at a press conference. The journalists apparently only used the first line and people use this version as an excuse that they couldn't have done anything about it. For professionals, however, the full law is essential. Things we develop shouldn't go wrong and there is much more than we think we can do to prevent things going wrong.