The with a single comparative always indicates that a reason is to be given, and must not be followed, like a plain comparative, by than.
He is the more willing to sanction Smith's appointment because he knows him well.
If we want to construct such a sentence with a than, we must omit the the, e.g.:
He is more willing to sanction Smith's appointment than he would be if he did not know him well.
The with a pair of comparatives always means "by so much as . . . by that much".
The nearer you get to the one, the further you are likely to find yourself from the other.