From Greg Bahnsen’s “Van Til’s Apologetic”:
If the “facts” (external events or states of affairs) are completely a matter of “chance”- random and unconnected, having no rationale, no preestablished order,
Here we see that you can not separate the facts from the interpretation of those same facts. For example if you say that the human beings came into existence by the a process of N number of random mutations, but cannot justify the predication of the those mutations since the presupposition is that they (“the mutations”) have no relationship between one mutation to another since they are all random, you have failed to demonstrate a rational conclusion to the premise that human beings came into being through evolution. Or to put it into more simplistic terms, you have assumed what you are trying to prove.