失去语言能力 meaning in Chinese

loss of speech

Now i cannot be sure of the approbation or disapprobation of a client who cannot speak , and as the object of his desire or his repugnance cannot be clearly proved to me , on account of his want of speech , my services here would be quite useless , and cannot be legally exercised .
现在，对一位不能讲话的委托人，我无法确定他准确意思，由于他失去语言能力，不能清楚地向我表明他的好恶，所以我在这儿所做了一切都不能算是合法的，即使做了也是无效的。 ”