把这一句，留给此刻的你
It is pretty clear that they are ineffective in stopping the course of thought at present, but they have not always been so in the past and we cannot be sure that they will not be so in the future.
很明显，它们目前在停止思想进程方面是无效的，但它们过去并不总是这样，我们不能肯定将来也不会这样。