Full Idea
Carnap's four criteria for giving a good explication are similarity to the explicandum, exactness, fruitfulness and simplicity.
Clarification
The 'explicandum' is the thing which is explicated by the 'explicans'
Gist of Idea
Good explications are exact, fruitful, simple and similar to the explicandum
Source
report of Rudolph Carnap (Logical Foundations of Probability [1950], Ch.1) by Wesley Salmon - Four Decades of Scientific Explanation 0.1
Book Reference
Salmon,Wesley C.: 'Four Decades of Scientific Explanation', ed/tr. Humphreys,Paul [Pittsburgh 2006], p.5
A Reaction
[compressed] Salmon's view is that this represents the old attitude, that the contribution of philosophy to explanation is the clarification of the key concepts. Carnap is, of course, a logical empiricist.