 There are several applications in which qualitative theories of probability might be useful, or even necessary. In some situations there are no frequencies available to use as estimates for the probabilities, or it might be practically impossible to obtain those frequencies. Furthermore, people are often willing to compare the probabilities of two statements (‘\(\phi\) is more probable than \(\psi\)’), without being able to assign explicit probabilities to each of the statements individually (Szolovits and Pauker 1978, Halpern and Rabin 1987). In such situations qualitative probability logics will be useful.