Today we are going to define and discuss the differences between an internal and an external critique of a view. This distinction is vitally important in a debate, since many people will switch between the two types of critique invalidly. First, an internal critique is a critique that assumes the truth of some premise or worldview in order to examine what would be the case if it were true. This is most often expressed as a type of reductio ad absurdum. It attempts to show there is a problem with the consistency of some view. It does not attempt to show whether or not the view is actually true, as a matter of fact. In this way, both someone who accepts the view and someone who rejects the view can discuss the critique without thereby committing themselves to the truth of the view. A frequent example of an internal critique is when a skeptic will bring up the slaughter of the Canaanites, for example. They will say, “How can an all-good and all-loving God order the slaughter of the Canaanites?” They want to know how such an order is consistent with the proposed character of God.
An external critique, on the other hand, does seek to criticize a view on matters of fact. External critiques will, like the internal critiques, not be committed to the truth of the proposition or view involved, but, unlike internal critiques, it will be committed to the falsity of those views. An external critique may or may not grant a consistency aspect to the view involved; this is strictly irrelevant. An example of this might be: “The Bible has been revised so many times there’s no possible way we know what is says!” The externalist’s claim, then, is that there is some truth about the world that contradicts a particular claim or view.
So why does this matter? Because many times, skeptics and new atheists will oscillate between an internal and external critique as if they were precisely the same critique. A recent example concerns Lawrence Krauss and his recent dialogues with William Lane Craig. Krauss asked Craig the question about the Canaanites, to which Craig responded in a way that showed such a thing was consistent. Krauss, remarkably, granted that such an action would be consistent on Craig’s view, but then demanded, “but is it true!?” Notice the switch? Such a switch is irrelevant; an atheist and a Christian alike can discuss the question because precisely what is at stake is whether or not the view is consistent! Knowing whether or not the proffered view of Craig is true is going to be an external critique. But in that case, Krauss will have to do more than merely raise the consistency issue. He will have to claim that, as a matter of fact, Craig’s solution is not true—and that, I think, is not forthcoming.
When someone criticizes your view of something, it is vitally important that you identify whether or not it is an internal or external critique. Doing so helps to focus the conversation. It should also result in better dialogues between the Christian and the unbeliever.
 A reductio ad absurdum is where one wants to reduce a view to absurdity by showing a contradiction arises from assuming its truth.
 It is irrelevant in most cases, anyway. Obviously, if the matter of fact under discussion is consistency, then it does matter.