Do you think that there are things humans cannot understand because our brains are limited? Philosopher Thomas Nagel was recently quoted as saying that there are surely truths that people cannot understand (and will never be able to understand), as "nine-year olds cannot understand Maxwell's equations". I don't think this is a good example: after all nine-year olds are very smart, and it seems to me that they just don't have the time and information to "understand Maxwell's equations" while they are still nine years old. Is there any reason why nine-year olds wouldn't understand those equations if they had a nine-year old brain (physically speaking) forever (always adding new information)? And what if such equations were explained to them? Anyway, I would like you to answer not about the example, but about the general issue. Of course there are things we will never know and cannot know (for instancel, many things that happened before humans existed, or in distant parts of the universe, or things people just didn't notice and left no trace of their existence). And some things we will never understand because it never happened, for circumstantial reasons, that somebody had the right idea (it could have happened that Einstein never existed to create relativity theory, and social or cultural circumstances could have been such that science and philosophy never came to existence, as they never have in many cultures). But all this has nothing to do with some essential limitation of human brains. Human brains are surely limited (they can store only some limited ammount of information, since there is a finite number of neurons, and they have some limited "processing velocity"), but this doesn't seem to be like being unable to understand something. By the way, we can store information in computers and take many generations to solve our questions. But even if some problems involve so many operations that we wouldn't have the time to solve them before the universe collapses (it seems that that's what happens with the question of mathematically perfect chess playing, since there are to many possibilities in chess), that is nothing like failing to understand chess, its rules, or the difference between good and bad chess moves. I apologize for having written so much. Thank you.