We're getting into deeply philosophical terrain here, Stu! I think I'm saying that science can't admit to unknowability in the natural word (I keep having to add in that qualification so as to exclude the supernatural). The advances we've made in the last fifty or a hundred years have been staggering, completely unpredictable a century ago. If there's a philosophy behind science, a large part of it must be stating that the quest for finding out what's really true will never end as long as there are human beings with brains. That's the beauty of science, and, implicitly, it also defines the ugliness of religion, which possesses certainties that science never wants to possess and, worse, which stop people from searching for what is really true. So you may be right that there are unknowable things that will never be known. But I'm not certain, and I doubt whether humanity will let the notion hinder the search for truth.