[Maursault]

No one argues that the Immaculate Conception is parthenogenesis. It could not possibly have been, because if it had, either Jesus would have been Jesusa, or Mary was hermaphroditic and Jesus her genetic clone. Since we know neither of these explanations is credible, it had to be miracle birth. When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.

Now with Horace and Isis it's quite different. Isis was a virgin and Horace was a falcon, so I'm really not sure how that worked.