The succession in which relations are generalized being thus determined, there result certain derivative principles to which this succession must more immediately and obviously conform.    The first is _the directness with which personal welfare is affected_. While, among surrounding things, many do not appreciably influence us in any way, some produce pleasures and some pains, in various degrees; and manifestly, those things of which the actions on the organism for good or evil are most decided, will, _cæteris paribus_, be those of which the laws of action are earliest observed.    Second comes _the conspicuousness of one or both phenomena between which a relation is to be perceived_. On every side are phenomena so concealed as to be detected only by close observation; others not obtrusive enough to attract notice; others which moderately solicit the attention; others so imposing or vivid as to force themselves on consciousness; and, supposing conditions to be the same, these last will of course be among the first to have their relations generalized.    In the third place, we have _the absolute frequency with which the relations occur_. There are coexistences and sequences of all degrees of commonness, from those which are ever present to those which are extremely rare; and manifestly, the rare coexistences and sequences, as well as the sequences which are very long in taking place, will not be reduced to law so soon as those which are familiar and rapid.    Fourthly has to be added _the relative frequency of occurrence_. Many events and appearances are limited to certain times or certain places, or both; {147} and, as a relation which does not exist within the environment of an observer cannot be perceived by him, however common it may be elsewhere or in another age, we have to take account of the surrounding physical circumstances, as well as of the state of society, of the arts, and of the sciences—all of which affect the frequency with which certain groups of facts are observable.    The fifth corollary to be noticed is, that the succession in which different classes of relations are reduced to law, depends in part on their _simplicity_. Phenomena presenting great composition of causes or conditions, have their essential relations so masked, that it requires accumulated experiences to impress upon consciousness the true connexions of antecedents and consequents they involve. Hence, other things equal, the progress of generalization will be from the simple to the complex; and this it is which M. Comte has wrongly asserted to be the sole regulative principle of the progress.    Sixth comes _the degree of concreteness, or absence of abstractness_. Concrete relations are the earliest acquisitions. Such analyses of them as separate the essential connexions from their disguising accompaniments, necessarily come later. The analyses of the connexions, always more or less compound, into their elements then becomes possible.