In the study of rhetoric, the term begging the question has a technical meaning that differs somewhat from its contemporary meaning in everyday speech. For Lewis, to beg the question is to assume the validity of a premise that has not been proven to be true, often goes unstated, and in most cases already assumes the conclusion of the argument to be true. In Miracles, one common instance of begging the question is when critics of miracles assume beforehand that miracles cannot happen because of the unproven premise that nature is all that exists, thus ensuring they arrive at the conclusion they already believe.

“Incarnation” is a doctrinal and theological term within Christianity. It refers to the belief that in the historical person of Jesus of Nazareth, God has become a man. More specifically, the second person of the Trinity, referred to in the New Testament as the Son of God or “the Word,” has assumed human nature in the person of Jesus, thus rendering Jesus both fully God and fully human. The usage of the term “incarnation” can refer to the actual event or the process by which this event took place (the miracle linked historically with the beginning of Mary’s pregnancy with Jesus), or more generally to the whole nature of Jesus’s identity and existence as portrayed in the biblical gospels.