According to the University of Leicester, critical evaluation includes approaching an issue from both sides and suggesting counter arguments to the points made in support of both. After a theory has been evaluated, it must be examined for weaknesses by trying to find evidence that disproves it.
A critical evaluation casts a verdict as to what extent statements within a piece of writing (such as an essay) are true. While something is being critically evaluated, it is important that facts be gleaned from a wide range of sources that both agree and disagree with the arguments being made.
The goal is to come up with the most important facts of the argument, to ascertain that they can stand up to close scrutiny and to justify making those choices.