conundrum

1. N-COUNT A conundrum is a problem or puzzle which is difficult or impossible to solve. 難解之謎[正式]

...this theological conundrum of the existence of evil and suffering in a world created by a good God. ...生存在良善之神所創(chuàng)造的一個(gè)邪惡和痛苦的世界這個(gè)神學(xué)難題。