Full Idea
The mark of perfect knowledge is that nothing appears in the thing under consideration which cannot be accounted for, and that nothing is encountered whose occurrence cannot be predicted in advance.
Gist of Idea
Perfect knowledge implies complete explanations and perfect prediction
Source
Gottfried Leibniz (On Wisdom [1693], 1)
Book Reference
Leibniz,Gottfried: 'Leibniz Selections', ed/tr. Wiener,Philip P. [Scribners 1951], p.79
A Reaction
I would track both of these back to the concept of perfect understanding, which is admittedly a bit vague. Does a finite mind need to predict every speck of dust to have perfect knowledge? Do we have perfect knowledge of triangles?