''So then, as, among all genethlialogical inquiries whatever, a more general destiny takes precedence of all particular considerations, namely, that of country of birth, to which the major details of a geniture are naturally subordinate, such as the topics of the form of the body, the character of the soul and the variations of manners and customs, it is also necessary that he who makes his inquiry naturally should always hold first to the primary and more authoritative cause, lest, misled by the similarity of the genitures, he should unwitting generally call, let us say, the Ethiopian white or straight-haired, and the German or Gaul black-skinned and woolly-haired, or the latter gentle in character, fond of discussion, or fond of contemplation, and the Greeks savage of soul and untutored of mind; or, again, on the subject of marriage, lest he mistake the appropriate customs and manners by assigning, for example, marriage with a sister to one who is Italian by race, instead of to the Egyptian as he should, and a marriage with his mother to this latter, though it suits the Persian. Thus in general it is needful first to apprehend universal conditions of destiny, and then to attach to them the particular conditions which relate to degree. In the same fashion likewise, dealing with the division of time, one must take as a basis in each single prediction the differences and special properties of the temporal ages, and see to it that we do not, in the ordinary, simple treatment of matters incident to the inquiry, carelessly assign to a babe action or marriage, or anything that belongs to adults, or to an extremely old man the begetting of children or anything else that fits younger men; but once and for all let us harmonize those details which are contemplated in temporal terms with that which is suitable and possible for persons in the various age-classes.'' -
http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Ptolemy/Tetrabiblos/4C*.html#10
No, you start with generalizations, and then make particularizations, since the particularizations are affected by the generalizations...