 However, hypotheses are not only probable but also indubitable when they explain something very clearly and easily, when our senses do not contradict them, when reason shows that the phenomenon in question could not occur otherwise and it is deduced from principles that are certain, and when the hypotheses serve not only to explain one single effect but many different and even distinct effects; for it would be impossible for hypotheses not to be found defective in some situation if they were not true. (H 218)