Vitae philosophorum

37. Among the things accounted just by conventional law, whatever in the needs of mutual intercourse is attested to be expedient, is thereby stamped as just, whether or not it be the same for all; and in case any law is made and does not prove suitable to the expediencies of mutual intercourse, then this is

no longer just. And should the expediency which is expressed by the law vary and only for a time correspond with the prior conception, nevertheless for the time being it was just, so long as we do not trouble ourselves about empty words, but look simply at the facts.