Rawlins stresses that it is impossible to prove a causal link between the drug and the deaths.

罗林斯强调无法证明这种药物和多起死亡事件之间存在因果关系。

He would dearly love to show a causal relationship between culture and imperialism, but cannot.

他倒是十分想揭示文化与帝国主义之间的因果联系，可是却无能为力。