We can't know everything; in fact, compared to the vast expanses of our ignorance, we can't really know very much. So the problem of "limiting knowledge" is not just one of the conflict between efforts to make knowledge available and efforts to keep knowledge locked up. There is also the often-invisible problem of how we decide what it is we are going to try to know, and what, as a consequence, we decide, even if by benign neglect, we are not going to know. This problem is particularly present in efforts to expand formal knowledge about the world through scientific research. In this essay I will briefly explore how this effort to expand knowledge brings with it, unavoidably and simultaneously, powerfully enforced limits on knowledge that are often unexamined.