Ed Feser gives a nicely articulated hermeneutic principle, stated below:

"The arguments of great philosophers of the past need to be understood, not only in the context of their times, but also in light of how later thinkers built on them. For an argument can contain, inchoately, real insights which only later thinkers were able to spell out adequately; and we will miss these insights if, overly fearful of anachronism, we insist pedantically on reading the argument in isolation from this later tradition. What ultimately matters in philosophy is not exactly who said exactly what, exactly when and exactly how. What matters is what is true, and whether an argument is likely to lead us to it. Anachronism, then, while a danger, is a less serious danger than loss of truth. To think otherwise is to abandon philosophy for mere scholarship. (Scholarship has its place, of course. But its place is to serve the ends of philosophy."

However, there must be some further principle whereby one is able to judge the strength (or defect) of the author in his original thought so as to distinguish the confused universal (or inchoately stated principle) from the determinate and distinctly stated interpretation. What is this principle? Here is one proposal. Here is mine (not necessarily in contradistinction to the prior proposal): philosophical wisdom.