 The methodological core thus consists in collecting relevant phenomena, finding analogies between them, and ascribing those analogies to similar causes, thereby reducing a variety of phenomena to regular principles underlying them (THN App.3, Abs.1, EHU 4.12)—while knowing that our knowledge cannot transcend what we can infer on an analogical basis from the effects themselves (THN I.8). Just as comparing rays of light reveals their determinable properties which, once determined, can be used in constructing explanations, the comparison of instances of human behavior reveals the principles of human nature with increasing generality and exactness. Salient human phenomena are collected from history and observation, then compared; if analogies and similarities are found, they are ascribed to some principle of human nature that are also compared, grouped and resolved into more general ones (see also Section 4.8 below). This process results in determinable properties of human nature like the faculties of reason, sympathy, moral sense etc.; determining how these properties are actually instantiated in different social, historical, individual, etc. circumstances provides the explanatory raw material for singular phenomena (EHU 8.7, 8.9). Thus we reach the principles of human nature that are the proper aim of inquiry in the science of man. These principles can be used, at the stage of synthesis, to explain why our impressions and ideas follow one another in the order they do.