What can we conclude from this brief history of cavitation in rubber-like solids? At first, the condition for internal cracking appeared to be particularly simple. Whenever a stress was set up equal to the maximum possible stress calculated from simple elasticity theory, i.e., 5E/6, then cavitation ensued. But it is now clear that this criterion is only approximately true and then only for a certain narrow range of void sizes. Because cavitation is often found under the originally deduced conditions, voids are obviously present in rubber of an appropriate size, between about 0.1 µm and 1 mm in radius, at least when the volume of rubber is large enough to accommodate them. Thus, even though the original criterion was arrived at on a faulty premise, it has proved to be a useful and broadly applicable fracture criterion. In preparing this brief historical review, I have been led to some elementary conclusions about research itself. First, the fact that a theory appears to work does not mean that it is true. Secondly, even simple, carefully-selected, systems are often difficult to understand. And, finally, contributions from different points of view are essential to scientific progress.