President Obama issued a proclamation for Father’s Day, Friday, but somewhere in the short statement he lost the plot.

The president begins by talking about the things fathers do for their children. Although his list does not seem different from what a mother would do, he does imply that the way a father does things is distinctive and necessary:

Fatherhood also carries enormous responsibilities. An active, committed father makes a lasting difference in the life of a child. When fathers are not present, their children and families cope with an absence government cannot fill. Across America, foster and adoptive fathers respond to this need, providing safe and loving homes for children facing hardships. Men are also making compassionate commitments outside the home by serving as mentors, tutors, or big brothers to young people in their community. Together, we can support the guiding presence of male role models in the lives of countless young people who stand to gain from it.

So far, so good. But then comes this ritual bow to family “diversity”:

“Nurturing families come in many forms, and children may be raised by a father and mother, a single father, two fathers, a step father, a grandfather, or caring guardian.”

Here he implies that practically any group of people inclusive of an adult male and a child constitutes a family, and that none of these combinations is inferior to any other. But that is not true. The family as a natural institution is based on a father and mother and their mutual offspring.

Where this structure breaks down owing to divorce or non-marriage or re-marriage, the father may parent alone or another male may take on the father role, but these are substitutes for the norm and, even when they function well, are not morally equivalent to it. (A widowed father is in a class of his own morally, I would think, but still not in a normal or ideal state.)

Furthermore, if “two fathers” is a valid form of the family, “two mothers” would have to be also. But a two-mother “family” excludes the father or father substitute that Obama implies in the rest of his speech is necessary for a child.

The oil spill speech was not popular, Mr President, but this one is actually harmful -- because the welfare of children is at stake.