
“Maternity," it has been said, "is a matter of fact, paternity is a matter of opinion.”
Ch. 4, Nation Making http://books.google.com/books?id=1ANBAQAAMAAJ&q=%22Maternity+it+has+been+said+is+a+matter+of+fact+paternity+is+a+matter+of+opinion%22&pg=PA122#v=onepage
Physics and Politics https://www.gutenberg.org/ebooks/4350 (1869)