"There is no law unless it be just". So the validity of law depends upon its justice. But in human affairs a thing is said to be just when it accords a right with the rule of reason: and as we have already sent,the first rule of reason is the natural law. Thus,all humanly enacted laws are in accord with reason to the extent that they derive from natural law. And if a human law is at variance in any particular with natural law,it is no longer legal, but rather a corruption of law."-St. Augustin.
Using the foregoing excerpt as your point of departure, explain the major differences between natural law thinkers and legal positivism.
Read them and get back to us. Then we will be able to fine tune your argument rather than invent it as you seem to want us to do here.