All forms of labour being therefore admitted to be honourable and necessary, there was no difficulty felt about justifying their reward. It was always common ground that services of all kinds were entitled to be properly remunerated, and questions of difficulty only arose when a claim was made for payment in a transaction where the element of service was not apparent.[1] The different occupations in which men were engaged were therefore ranked in a well-recognised hierarchy of dignity according to the estimate to which they were held to be entitled. The Aristotelean division of industry into _artes possessivae_ and _artes pecuniativae_ was generally followed, the former being ranked higher than the latter. 'The industries called _possessivae_, which are immediately useful to the individual, to the family, and to society, producing natural wealth, are also the most natural as well as the most estimable. But all the others should not be despised. The natural arts are the true economic arts, but the arts which produce artificial riches are also estimable in so far as they serve the true national economy; the commutation of the exchanges and the _cambium_ being necessary to the general good, are good in so far as they are subordinate to the end of true economy. One may say the same thing about commerce. In order, then, to estimate the value of an industrial art, one must examine its relation to the general good.'[2] Even the _artes possessivae_ were not all considered equally worthy of praise, but were ranked in a curious order of professional hierarchy. Agriculture was considered the highest, next manufacture, and lastly commerce. Roscher says that, whereas all the scholastics were agreed on the excellence of agriculture as an occupation, the best they could say of manufacture was _Deo non displicet_, whereas of commerce they said _Deo placere non potest_; and draws attention to the interesting consequence of this, namely, that the various classes of goods that took part in the different occupations were also ranked in a certain order of sacredness. Immovables were thought more worthy of protection against execution and distress than movables, and movables than money.[3] Aquinas advises the rulers of States to encourage the _artes possessivae_, especially agriculture.[4] The fullest analysis of the order in which the different _artes possessivae_ should be ranked is to be found in Buridan's _Commentaries on Aristotle's Politics_. He places first agriculture, which comprises cattle-breeding, tillage, and hunting; secondly, manufacture, which helps to supply man's corporal needs, such as building and architecture; thirdly, administrative occupations; and lastly, commerce. The Christian Exhortation, quoted by Janssen,[5] says, 'The farmer must in all things be protected and encouraged, for all depend on his labour, from the monarch to the humblest of mankind, and his handiwork is in particular honourable and well pleasing to God.'