What if he did not know who his father was? Is the child of a US citizen mother, with an unidentified father, a natural born citizen according to your definition?
Is the child of a US citizen mother, with an unidentified father, a natural born citizen according to your definition?
I would say that until a father was identified the child would be a citizen, but not a natural born citizen. There wouldn't be enough evidence to come to that conclusion.
Would you consider the mother of such a child a tramp or just a young woman who made a mistake?