The 1939 and 1965 versions of the Restatement of Torts included the substantial contributing factor test as an alternative standard for determining causation. But this doctrine was dropped by the Restatement (Third) of Torts (2010), and the rationale for this switch persuaded the Supreme Judicial Court of Massachusetts to conclude that “the traditional but-for factual causation standard is the appropriate standard to be employed in most cases, including those involving multiple alleged causes,” because “the substantial …