There is absolutely no such principle or reason; it is utterly unreasonable or illogical.
你竟然说他会做这种事情，这简直是断无此理，他一向正直无私。
You actually claim he would do such a thing; that's utterly unreasonable, he has always been upright and selfless.
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There is absolutely no such principle or reason; it is utterly unreasonable or illogical.