 We have already seen that Aristotle is not committed to the view that everything has all four kinds of causes, Rather, his view is that a scientific explanation requires up to four kinds of causes. We may illustrate this point with the help of an example. Consider, in particular, the case of a lunar eclipse. In the Metaphysics, Aristotle says that an eclipse of the moon does not have a final cause (Metaph. 1044 b 12). He also says that, strictly speaking, a lunar eclipse does not have matter. Rather, it has a cause that plays a role analogous to matter. This second claim can be inferred from what Aristotle says about the things that exist by nature but are not substances. With respect to these things, Aristotle says that they do not have matter but rather something that underlies (Metaph. 1044 b 8–9). In the case of a lunar eclipse, that which underlies is the subject affected by the eclipse, that is, the moon. The moon is not strictly speaking the matter of the eclipse but rather the subject that undergoes an eclipse when the earth comes in the middle between the moon and the sun. Should we give the earth as the efficient cause of a lunar eclipse? We have to be careful here. By saying that the moon is a deprivation of light caused by the earth, we distinguish this particular deprivation of light from other kinds of deprivation of light. Still, by citing the earth as the efficient cause of a lunar eclipse, we are not yet giving the most precise description of the efficient cause. More directly, we are not yet saying what the earth is doing to cause a lunar eclipse. A lunar eclipse is a deprivation of light caused by the interposition of the earth between the sun and the moon. By coming in the middle of the moon and the sun the earth blocks the light and causes the moon to suffer an eclipse. Hence, it is the interposition of the earth between the sun and the moon is the proximate efficient cause of a lunar eclipse. Citing the proximate efficient cause is also giving the most accurate description, and indeed the full explanation, of a lunar eclipse. (An insightful discussion of how Aristotle explains natural phenomena such as a lunar eclipse and sleep can be found in Code 2015: 11–45).