In general the evaluation of a philosopher should be integrated with an attempt to understand him. If, on a given interpretation, he has said something obviously foolish, it is usually worth looking for an alternative interpretation, However, if on reflection an author seems to you to be mistaken, you should not hesitate to draw this conclusion. There are special problems which arise when dealing with philosophers of earlier periods, especially when they wrote in foreign languages. You cannot assume, without knowledge of their language and culture, that you have come to terms with them adequately. It is extremely difficult to interpret such thinkers in depth or detail.
Translations can be misleading.
It is often instructive to consult several different translations of a single passage, to see what a vital difference the translator can make to the sense. Mere summary of a writer's position is Inadequate and should be distinguished from creative exposition of his text. The most effective presentation of his view, even if you are going to attack itp is a sympathetic exposition. There is nothing objectionable about devoting an entire essay to the interpretation of a difficult work or passage, illuminating the structure of an argument, e.g., by using one passage to throw light upon the meaning of another, or by exploring an author's use of key terms. Constructive philosophical scholarship demands no less creativity than destructive polemic.