Many critics of Christianity have cited the violent acts of Christian nations as a reason to denounce the religion. Science-fiction writer Arthur C. Clarke said that he could not forgive religions for the atrocities and wars over time. Richard Dawkins makes a similar case in his book, "The God Delusion". In the counterargument book "The Dawkins Delusion?," Alister McGrath responds to Dawkins by suggesting that, far from endorsing "out-group hostility", Jesus commanded an ethic of "out-group affirmation". McGrath agrees that it is necessary to critique religion, but says that Dawkins seems unaware that it possesses internal means of reform and renewal. While Christians may certainly be accused of failing to live up to Jesus' standard of acceptance, it is there at the heart of the Christian ethic.