  The last example is particularly important because it illustrates the intimate connection between ḥads and tajriba, a connection maintained by Ibn Kammuna (and others) throughout. Tajriba is the most usual justification for the knowledge claimed by astrologers and alchemists. Hence both ḥads and tajriba aim to function as sources for hidden knowledge within scientific systems that are based upon (ultimately) Aristotelian logic. Although it is repeatedly invoked as the source for scientific knowledge, ḥads is not a tool of scientific inquiry, but rather a way of explaining, post facto, how a thinker hit upon the solution to a difficult problem. As such its function in science is very much the same as its function in explaining religious inspiration and prophecy.