But for us, to whom He has given also the faculty, these things are not sufficient; for unless we act in a proper and orderly manner, and conformably to the nature and constitution of each thing, we shall never attain our true end. For where the constitutions of living beings are different, there also the acts and the ends are different. In those animals, then, whose constitution is adapted only to use, use alone is enough: but in an animal which has also the power of understanding the use, unless there be the due exercise of the understanding, he will never attain his proper end. Well then God constitutes every animal, one to be eaten, another to serve for agriculture, another to supply cheese, and another for some like use; for which purposes what need is there to understand appearances and to be able to distinguish them?