The popular conception of science says that science is a collection of observable facts that anybody can verify for himself. We have seen that this is not true in the case of expert knowledge, like that needed in diagnosing a disease. More over it is not true in the physical sciences. In the first place, for instance, a layman cannot possibly get hold of the equipment for testing a statement of fact in astronomy or in chemistry. Even supposing that he could somehow get the use of an observatory or a chemical laboratory, he would not know how to use the instruments he found there and might very possibly damage them beyond repair before he had ever made a single observation. So it is misleading to describe science as a collection of facts.