Cicero's claim about immutable goodness

There is a train of thought going back even to the classical and ancient world that living an upright life is one of the marks of being human, and that going against it is an offense against humanity and ourselves. Here is the Roman writer Cicero (d. 43 BC), giving eloquent voice to that thought:

There is a true law, a right reason, conformable to nature, universal, unchangeable, eternal, whose commands urge us to duty, and whose prohibitions restrain us from evil. Whether it enjoins or forbids, the good respect its injunctions, and the wicked treat them with indifference. This law cannot be contradicted by any other law, and is not liable either to derogation or abrogation.
Neither the senate nor the people can give us any dispensation for not obeying this universal law of justice. It needs no other expositor and interpreter than our own conscience. It is not one thing at Rome and another at Athens; one thing today and another tomorrow; but in all times and nations this universal law must for ever reign, eternal and imperishable. It is the sovereign master and emperor of all beings. God himself is its author,—its promulgator,—its enforcer. He who obeys it not, flies from himself, and does violence to the very nature of man. For his crime he must endure the severest penalties hereafter, even if he avoid the usual misfortunes of the present life.

[Alternate translation of the last portion:
Whoever is disobedient is fleeing from himself and denying his human nature, and by reason of this very fact he will suffer the worst penalties, even if he escapes what is commonly considered punishment.]

[The second seems a more faithful rendering of that portion of the original, which is given as:]
cui qui non parebit, ipse se fugiet ac naturam hominis aspernatus hoc ipso luet maximas poenas, etiamsi cetera supplicia, quae putantur, effugerit.

– Marcus Tullius Cicero (De Re Publica [Of The Republic], Book III Section 22)

Some themes are common to all humanity. Cicero had a good reputation in the church, both for his philosophy and for his writing style. 

So: Do we obey a command because God gives it, or do we obey a command from the incentives of reward and punishment? That question, much like Euthyphro's dilemma, also has premises that undermine a complete answer. If the desire to do right is intrinsic to humanity, and if there are universals of what is right, then denying them is denying part of our humanity. In that case, doing what is right is healthy and intrinsically carries the reward of actualizing the human potential even if no external incentives ever appear. Likewise doing is wrong is unhealthy and intrinsically carries the shame and loss of rejecting that part of our own humanity, even if no external punishments are ever applied.

From a Christian point-of-view, we identify this intrinsic good with both God's will and God's nature. This means that pursuing this intrinsic good will move us closer to God's will and nature, and that turning away would do the opposite. And because fellowship is built on what is shared and common, the same pursuit of intrinsic good will unite us more closely with people who pursue the same goals.

If Cicero is right that there exist human moral universals, then a denial or rejection of these human moral universals would lead to an erosion of humanity or human excellence. It would also lead to an erosion of unity in society, as each group goes after their own way, and an erosion of the rule of law as it is considered to have no ultimate validity.

Is Cicero right? We live in an age that no longer grants his premises. (Which, I hope, will be the topic of the next post.)