Full Idea
Just as unpredictability does not entail inexplicability, so predictability does not entail explicability.
Gist of Idea
Unpredictability doesn't entail inexplicability, and predictability doesn't entail explicability
Source
Alasdair MacIntyre (After Virtue: a Study in Moral Theory [1981], Ch. 8)
Book Reference
MacIntyre,Alasdair: 'After Virtue: a Study in Moral Theory' [Duckworth 1982], p.97
A Reaction
The second half is not quite as obvious as the first. The location of lightning strikes is an example of the first. He gives examples of the second, but they all seem to be very complex cases which might be explained, if only we knew enough.