A friend and I (we both DM for each other occasionally) are having a discussion about where the increases in power of divine (cleric and paladin) and psuedo-divine (warlock) classes comes from at level ups.
I'm under the impression that these classes are chosen by the gods (or their patron), and granted immense power early, but must learn to harness it as they grow. Levels happen to be discrete times when the mechanics of character growth match up with the "learned" abilities of the caster. From the cleric section of the PHB:
A cleric might learn formulaic prayers and ancient rites, but the ability to cast cleric spells relies on devotion and an intuitive sense of a deity's wishes (PHB 56)
This to me, reads as if a cleric's power grows as his devotion grows, and that devotion is denoted in-game as discrete levels.
To him, these classes are granted additional power by their gods at each level up. Their god (or patron) takes favor to them, and bestows greater powers upon them as needed. He quotes:
The gods don't grant this power to everyone who seeks it, but only to those chosen to fulfill a higher calling. (PHB 56)
This seems to show that the powers and their use is governed by the gods, and not the cleric's own power in any respect.
Both of these passages seem a bit ambiguous, and could be interpreted in ways that support either arguement. Is there any additional evidence in any official source that reveals where the powers granted to these classes comes from at each level up?