Human Development and Family Science is a social science discipline frequently and incorrectly assumed to be a matter of common sense. In truth, widespread social problems with development and relationships suggest that common sense is not actually very helpful in this domain. And it is not common at all, as disagreements over basic principles of development and relationship are typical. HDFS is not “just common sense.” Professional expertise, on the other hand, is defined by knowledge that is broader and deeper than common sense, and is produced through scientific literacy.