The contradictions between the lists have been used to question the accuracy of the gospel accounts since ancient times, and several early Christian authors responded to this. Augustine, for example, attempted on several occasions to refute every criticism, not only because the Manichaeans in his day were using the differences to attack Christianity, but also because he himself had seen them in his youth as cause for doubting the veracity of the Gospels. His explanation for the different names given for Joseph's father is that Joseph had a biological father and an adoptive father, and that one of the gospels traces the genealogy through the adoptive father in order to draw parallels between Joseph and Jesus (both having an adoptive father) and as a metaphor for God's relationship with humankind, in the sense that God "adopted" human beings as his children.