In investigations of nature, however, it is necessary not only to consider the changeable understood universally according to its common features, but it is necessary to get down to details so that the primary agent in each individual case may be ascertained, especially in sensible, animate things, because in investigations of nature we must discover the universal principles through singulars, since in such investigations the particulars are better known than the universals. It is through the singulars that we come to believe that it is convenient and necessary for universals and their principles to exist, since it is only those universals which are exemplified in particulars that we accept, while those which are not exemplified in particulars, we reject.
[Albert the Great, De animalibus IX tr. 2, c.4, ed. HernannStadler, in: BGPhlvfA5, Munster9 16'.T21, ll.16-21m as quoted in Leen Spruit, "Albert the Great on the Epistemology of Natural Science", p. 64.]