Basic political words (including the word “political”) tend to be appropriated by diverse movements and parties over time, which causes them to accumulate diverse and even opposite meanings. “Liberal” is a great example.
Another example is “republic,” which is now millennia old and appears in the official names of major parties as well as 110 sovereign states (by my count), ranging from the Laos People’s Democratic Republic to the Islamic Republic of Afghanistan and including such odd couples as both of the Koreas.
Some would say that any real republic is a regime with a popular or majoritarian element that is limited by checks and balances and restraints on the powers of government. These limits distinguish it from a democracy. That usage is not wrong, but it doesn’t necessarily track the terminology of the US founders. For instance, Jefferson defined a republic as a “government by its citizens in mass, acting directly and personally, according to rules established by the majority; and … every other government is more or less republican, in proportion as it has in its composition more or less of this ingredient of the direct action of the citizens.” As the image shows, many of Jefferson’s contemporaries agreed that a republic was a democracy.
For others, a republic is a system in which the people own and control the most important goods. That is why communist states have generally named themselves republics. One justification may be etymology. The Latin phrase res publica means the public’s thing (or good, or wealth, or interest). Thus, if you believe that things like factories and farms should be public property, you may be inclined to use the word “republic.” In addition, the French revolution has often inspired communists and other left radicals. That revolution called itself “republican.” There is also a less prominent tradition of radical commonwealth thought in English; and “commonwealth” is a direct translation of res publica.
For some political theorists of the last 30 years (e.g., Philip Pettit, Ian Shapiro) republicanism means opposition to domination, which is arbitrary power over others. A republic is a regime that successfully combats domination, and modern republicans debate the necessary and ideal tools for that end. Rule of law, popular participation and responsive government, civil liberties, and checks and balances are among the options.
A different school of modern theorists see a republic as a regime that expects a particularly high degree of virtue from its citizens. For instance, Hannah Arendt defines a republic as a community that allows and expects participants to display civic virtues in public forums.
Until recently, I would have held onto one fixed point. I would have proposed that any definition of republic should cover the regime that governed Rome between the overthrow of the kings and the reign of emperor Augustus and his successors, because the word first arose to name that system. In analyzing the Roman republic, we might prefer to emphasize its appreciation of civic virtues, its empowered populace, its mixed constitution with limited popular power, its defense of private rights, its public property (the forum, the army), or its commitment to rule of law and other protections against domination (for free men)–but one way or another, we would have to tie our definition to the ancient regime. And a monarchy would be incompatible with a republic, since the Roman republic is what we call the interlude between the era of kings and that of emperors. Today, most of the countries that do not call themselves republics are monarchies.
But then I read Anthony Kaldellis, The Byzantine Republic: People and Power in New Rome (Harvard, 2015). Kaldellis shows that almost all Romans believed that their republic persisted under the emperors. The structure of its government changed, but Rome remained a republic–indeed, until 1453. To call a limited period of Roman history “the republic” is to impose modern terminology on the past.
I suspect that one reason that many moderns have believed that the emperors ended the Roman republic is Tacitus. He is a superb author, enormously valuable and timely, but he does have an ax to grind. As a senator and a member the hereditary senatorial class, Tacitus views the emperors’ usurpation of the Senate’s powers as a fundamental blow to liberty. In modern times, his account has been a powerful inspiration for anyone who wants to defend representative legislatures against tyrants. But the Roman senate was never representative; it was oligarchical. Other Romans could disagree with Tacitus that weakening the Senate really undermined the republic. For many of them, the defining feature of a republic (per Kaldellis) was its coherence as a community. Some Romans viewed emperors as good guardians of their community, in which case the republic could thrive under Augustus or his successors. Their main concern was whether a given monarch really served the public good; if not, he was illegitimate.
The conclusion, for me, is that “republic” can mean many different things, and no one should assert that it has only one true meaning. I am interested in anti-domination and civic virtue and prefer to use the word “republican” for combinations of those ideas. But mainly, one should define and clarify one’s terms.
See also: do we live in a republic or a democracy?; civic republicanism in medieval Italy: the Lucignano council frescoes; The French Republic denounces the French State; citizens against domination; James Madison in favor of majority rule etc.