In one way or another, many (or maybe even all) arguments from analogy can be seen as inferences to the best explanation. But they are usually incomplete explanations. The argument for life on other planets did not have to com- mit itself to any particular theory about the origin of life or about which conditions are needed to support life. Nor did the car argument specify exactly what makes cars reliable. Such arguments from analogy merely list a number of similarities so that the list will be likely to include whatever factors are needed for life or for reliability. In this way, arguments from analogy can avoid depending on any complete theory about what is and what is not relevant.
This incompleteness makes arguments from analogy useful in situations where we do not yet know enough to formulate detailed theories or even to complete an inference to the best explanation. Yet the incompleteness of ar- guments from analogy also makes them more vulnerable to refutation, since the analogies that they list might fail to include a crucial respect.