According to the formal unphilosophic method of the sciences, definition is the first desideratum, as regards, at least, the external scientific form.
 
The positive science of right, however, is little concerned with definition, since its special aim is to give what it is that is right, and also the particular phases of the laws. For this reason it has been said as a warning, Omnis definitio in jure civili periculosa;  and in fact the more disconnected and contradictory the phases of a right are, the less possible is a definition of it. A definition should contain only universal features; but these forthwith bring to light contradictions, which in the case of law are injustice, in all their nakedness. Thus in Roman law, for instance, no definition of man was possible, because it excluded the slave.