It's a supposition that whatever the object of theory might be, - theory itself must-- owing to whatever intellectual constraints one can imagine-- be of such and such a form.

不管理论是关于什么事物的，它自己都只能-,由于人们思想的局限性-,以猜想的形式存在。

耶鲁公开课 - 文学理论导论课程节选

It's an hypothesis about something, the exact nature of which one needn't necessarily have in view.

它是关于某种事物的假说，由于人们思想的局限性。

耶鲁公开课 - 文学理论导论课程节选