expansion of thought- Hume

“It seems a proposition, which will not admit of much dispute, that all our ideas are nothing but copies of our impressions, or, in other words, that it is impossible for us to think of any thing, which we have not antecedently felt, either by our external or internal senses."



I am a bit confused when it comes to this. It seems to me that Hume once said that our thoughts can be expanded upon. But here it seems that Hume is saying that what we have installed in our brains are our only limits of thinking, that he believes, like Locke maybe, that we have a clear slate in our minds and until we have experienced through our senses, it is then that we know about it. Maybe we only know, and are only capable of thinking what we already know? Or are we capable of thinking beyond.