Let us illustrate Wagner's mature use of Leitmotif by the theme which happens to be associated with Alberich's ring.
The Rhine-daughters have been teasing the Nibelung Alberich, and are rejoicing in the light of the Rhine-gold which shines at the top of a rock as the sun strikes it through the water.
Alberich does not think much of the gold if its only use is for these waterchildren's games.
What it becomes in the mind of the Nibelung is grimly evident when Alberich uses his ring in Nibelheim.
After Abelard's retirement, John carried on his studies under Alberich of Reims and Robert of Melun.