approfondir

to deepen; to consider more thoroughly, to delve deeper into

“Avec ces propos et d’autres semblables, le pauvre gentilhomme perdait le jugement. Il passait les nuits et se donnait la torture pour les comprendre, pour les approfondir, pour leur tirer le sens des entrailles, ce qu’Aristote lui-même n’aurait pu faire, s’il fût ressuscité tout exprès pour cela.” — With these passages and other similar ones, the poor gentleman lost his judgement. He spent his nights and tortured himself to understand them, to consider them more deeply, to take from them their deepest meaning, which Aristotle himself would not have been able to do, had he been resurrected for that very purpose.

From a- + profond + -ir.