formularies. He holds, nonetheless, that penal substitution can be described as a model in a way comparable to how physics uses the term. He defines the term model, in a theological sense, as "explanatory constructs formed to help us know, understand, and deal with God, the ultimate reality." He states that the "mystery of God is more than any one model, even the best, can express." He states that "all the knowledge we can have of the atonement is of a mystery which we can only think and speak by means of models." To Packer, the biblical models are presented as being inspired by God and given to us as "knowledge of the mystery of the cross." The theologian Stephen Sykes has interpreted Packer's account of penal substitution as being presented as a metaphor. Theologians who advocate penal substitution are keen to define the doctrine carefully, rather than, as Packer says; "the primary question is, not the rationality or morality of God but the remission of one's sins." He suggests that it be seen not as a mechanical explanation (how it works) but rather than kerygmatically (what it means to us). Denney contends that the atonement should not be seen forensically (though as Packer says, Denney avoided the term "penal" in any case). What matters in Packer's view is that "Jesus Christ our Lord, moved by a love that was determined to do everything necessary to save us, endured and exhausted the destructive divine judgment for which we were otherwise inescapably destined, and so won us forgiveness, adoption and glory." However, John Stott critiques loveless caricatures of the cross as "a sacrifice to appease an angry God, or ... a legal transaction in which an innocent victim was made to pay the penalty for the crimes of others" as being "neither the Christianity of the Bible in general nor of Paul in particular." Furthermore, "It is doubtful if anybody has ever believed such a crude construction." Contemporary controversies Controversy has arisen over a statement made by Steve Chalke that "The cross isn't a form of cosmic child abuse—A vengeful Father punishing his Son for an offense he has not even committed." This sparked a debate in the UK among evangelicals which is cataloged in the book The Atonement Debate: Papers from the London Symposium on the Theology of Atonement (Zondervan, 2008). The debate has largely been conducted in evangelical circles,