A Florida Supreme Court case raises fundamental questions about the nature of fatherhood and legal responsibilities. Sixteen months after his divorce, Richard Parker made a devastating discovery. A DNA test revealed that his 3-year-old son had been fathered by someone else. Mr. Parker immediately filed a lawsuit claiming fraud by his apparently unfaithful ex-wife. He took his case all the way to the Florida Supreme Court. Last week, the Florida justices ruled 7-0 against him. They said that Parker must continue to pay $1,200 a month in child support because he had missed the one-year postdivorce deadline for filing his...