The meaning in English translates to: "To each his own". What can that possibly mean? Hasn't it been perverted by such types as Marx?

From Wikipedia: Antiquity[edit]
The Latin phrase relates to an old Greek principle of justice which translates literally into English as "to each his own". Plato, in Republic, offers the provisional definition that "justice is when everyone minds his own business, and refrains from meddling in others' affairs" (Greek: "...τὸ τὰ αὑτοῦ πράττειν καὶ μὴ πολυπραγμονεῖν δικαιοσύνη ἐστί...", 4.433a). Everyone should do according to his abilities and capabilities, to serve the country and the society as a whole. Also, everyone should receive "his own" (e.g., rights) and not be deprived of "his own" (e.g., property) (433e).

The Roman author, orator and politician Marcus Tullius Cicero (106 BC – 43 BC) popularised the Latin phrase:

"Iustitia suum cuique distribuit." ("Justice renders to everyone his due.") - De Natura Deorum, III, 38.
[...] ut fortitudo in laboribus periculisque cernatur, [...], iustitia in suo cuique tribuendo." (" [...] so that fortitude (courage) may be seen in hardship and danger, [...], justice in attributing to each his own".) - De Finibus Bonorum et Malorum, liber V, 67.
The phrase appears near the beginning of Justinian's Institutiones: iuris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere. (Inst. 1,1,3-4). (Translated into English: "the precepts of law are these: to live honestly, to injure no one, [and] to give to each his own".)

So there's a bit more on the phrase.

NOW: How did Marx et al (whoever?) pervert that?

The phrase appears near the beginning of Justinian's Institutiones: iuris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere. (Inst. 1,1,3-4). (Translated into English: "the precepts of law are these: to live honestly, to injure no one, [and] to give to each his own".) — Bitter Crank

This is a quote attributed to Cicero, my esteemed ancestor. Well, forerunner. Precursor, say.

NOW: How did Marx et al (whoever?) pervert that? — Bitter Crank

Being perverts, they pervert. Qui pervertit pervertant??

This is a quote attributed to Cicero, my esteemed ancestor. Well, forerunner. Precursor, say. — Ciceronianus the White

What does he mean by saying "Suum cuique"?

What does he mean by saying "Suum cuique"? — Posty McPostface

Cicero used the phrase in referring to the law, and "justice." I would say he refers to the need for the law to treat people fairly, impartially, by not favoring one person over another in applying the law. All are equal under the law, and what is due to each under the law is its impartial application. Rights and privileges granted by the law are granted to each person.

That was the idea. In fact, slaves were treated differently from those who were free. Roman citizens had privileges others did not. Citizenship was potentially available not merely to Romans but to all those damn non-Romans as well. So, St. Paul for example when being dragged away by a centurion supposedly said "I am a Roman citizen" (civis Romanus sum), thereby asserting his legal status as a Roman citizen which gave him a right to an appeal to the Emperor. He got his appeal for all the good it did him; he was sent to Rome and imprisoned until Nero or his surrogate got to his case and he was duly executed.

Later, in 212 A.D. or C.E., the reputedly cruel Emperor Caracalla, famous for his baths, extended Roman citizenship to all free men in the empire by edict. Before then, although it was gradually and fitfully extended over time, it was usually limited to inhabitants of Italy and those throughout the empire who had been awarded citizenship due to their prominence or by special favor.

Cicero used the phrase in referring to the law, and "justice." I would say he refers to the need for the law to treat people fairly, impartially, by not favoring one person over another in applying the law. All are equal under the law, and what is due to each under the law is its impartial application. Rights and privileges granted by the law are granted to each person. — Ciceronianus the White

Plato, in Republic, offers the provisional definition that "justice is when everyone minds his own business, and refrains from meddling in others' affairs" (Greek: "...τὸ τὰ αὑτοῦ πράττειν καὶ μὴ πολυπραγμονεῖν δικαιοσύνη ἐστί...", 4.433a). Everyone should do according to his abilities and capabilities, to serve the country and the society as a whole. Also, everyone should receive "his own" — Bitter Crank

What do you think about the Platonic interpretation, Ciceronianus and BitterCrank?

Cicero phrased the question as so:

suum cuique pulchrum est — Cicero

To each his own is beautiful. (Cicero)

What does he mean by this in philosophical terms?

"justice is when everyone minds his own business, and refrains from meddling in others' affairs" — Bitter Crank

Sure; it's none of my business if you prefer Bach or heavy metal. It's your own affair. I have no stake in your becoming a vegetarian or a Methodist. It's not for me to decide whether you should like cats better than dogs, or guernsey cows more than holsteins.

Sometimes, however, the health and safety of the community requires that we meddle in other people's affairs. When we see probable evidence of potential criminal activity (like traffic patterns that indicate a building may be operating as a whore house, or a crack house, or an illicit drug lab) then we should meddle in that buildings owners' and occupants' affairs so far as reporting to the police what we have observed.

I might consider it my business if you are violating the watering ban during a drought. I might meddle in your green grassy affairs by reporting you to the water district. If you have several cars parked on your yard for several weeks, I might consider it worth while to report you to the housing office to investigate your violations of laws about storing dead cars on yards in residential neighborhoods. If I see your children regularly not being in school, I might want to report you to child welfare.

What do you think about the Platonic interpretation, Ciceronianus and BitterCrank? — Posty McPostface

To the extent I can judge from what is quoted by Bitter Crank (I'm too lazy to read any Plato), I would call it simple-minded and incomplete. Justice isn't minding your own business unless the failure to mind your own business morphs into seeking to control the business of others--something Plato seemed to favor and inclined to do judging from his Republic. There's a difference between not being a busybody and being just.

RE: suum cuique pulchrum est

I can find reference to suum cuique in Cicero as per the post above (from Wikipedia) in De Natura Deorum, III, 38.

However, I cannot find any evidence of the longer expression suum cuique pulchrum est (which has a different meaning to the sense found in De Natura Deorum) being reliably associated with Cicero (or anyone else for that matter).

Thoughts or guidance on this welcome! :-)