It is more complete to say that human knowledge is limited by the human sub-conscious. The senses send in signals which are modified, deleted or passed on unchanged by the sub-conscious. One of its more complex (and mysterious to me) modifications is to change stray light rays into an excellent 3-D virtual reality (bats do the same thing but with reflected sound waves). Our human consciousness can be seen as a bubble in our sub-conscious. Our knowledge is prejudiced towards our darwinian objectives. For example, we are always looking for causes which give us more survival power.