"Authoritarianism", "totalitarianism", "dictatorship" - these terms are often thrown around as if there is no distinction between them. Quite the opposite is true, as we should acknowledge if we want them to remain a useful heuristic. To Plato the tyrant was "wolf in human form", but this philosopher was concerned with introducing into the political life of the polis something akin to our modern concept of authority. This is no surprise, because it is through the Greeks that the concept came to be recognised by the Romans, and then passed down to the Western tradition wherever the Pax Romana had been enforced.
The difference between the tyrant and the authority lies in where they derive their power, and how they exercise it. The tyrant is almost always concerned with the interests of himself, and tyranny can be seen as one of the egalitarian forms of government - everyone below him is equally worthless. A tyranny operates through fear and violence and totally outside the rule of law, which he will not usually even make a pretense to respect. Authoritarian rulers, by contrast, are always bound by some rule of law, however Draconian this rule may be. It is from this that they derive their legitimacy. This is not government by persuasion (the usual Greek way of running affairs), nor by violence (which would have destroyed Greek political life as they understood it), but another way of human living-together. The question the Greeks were unable to answer was where to derive "authority" from.
The source of authority must always be over and above the actual exercisers of power, who are acting in its name. Plato wished to implement the rule of the philosopher King who derived his legitimacy from self-evident truths, the sky of ideas that stretch over human affairs. Aristotle drew his example from the field of education, noting that the natural divison of the young and the old left the old more predisposed to rule for being wiser, and hence with authority. Plato was aware that only a small fraction of the polis was able to understand the authority of reason, and thus turned to religious myths to keep the rest in check. He mooted the idea of an afterlife with eternal rewards or punishments (which was not part of the Christian dogma until the 5th century AD, for reasons we shall return to below). Religion had become intertwined with traditional authority, and would remain so until the start of the modern era.
When the Romans chose the Greek philosophy as their guiding light (the only great philosopher the Romans had was Augustine), they venerated it as inviolate tradition. And it was under them that the concept of authority flourished and was merged once and for all with religion and tradition. The central political experience of the Romans was the founding of the city of Rome, and the duty of all subsequent statesmen was to augment the founding. They ruled the rest of the world as a sort of hinterland to the city, never repeating this central experience. To the Romans, religion meant literally to be tied back to the glorious past, especially by their most divine of divinities, Janus. The elders and rulers derived their authority by transmission from the past, which was the seat of it that existed outside of their current power. This is why to the Romans history was a set of examples and precedents for their statesmen to follow.
The foundation of Rome was augmented for a great length of time, but eventually it faltered. The torch was passed to the Roman Catholic Church, which made the life, birth, death and resurrection of Jesus Christ its new foundation experience. Thus, as the Roman Empire collapsed, the trinity of authority, tradition and religion was maintained. The Church was the source of authority, by which it delegated power to the secular princes of the world. It provided the moral yardstick which was used to judge the secular affairs of men, and with the impetus of eternal punishment in Hell duly applied, shaped the political realm for over a millennium. The introduction of the Platonic idea of hell into Christian thought assured its dominance in any contest with secular powers for a long time to come. But eventually it broke down.
It broke down of course under the secular advance of the modern natural sciences. It also broke down when the political children of the Enlightenment brought about their revolutions, destroyed tradition and authority, and were faced afresh with the problem that had confronted the Ancients: how to control the masses who would not listen to reason? It was concluded that the only way to do so was to maintain that single strand of the trinity, religion. But without the others, and when its usefulness was blatantly exposed by its preservation, it foundered. That the unprecedented brutality of the the twentieth century shortly followed can scarcely be deemed a coincidence.
The destruction of the trinity means we are confronted anew with the problem of how to deal with some of the most fundamental problems of human living-together. Hannah Arendt said that the liberal measures the decline of freedom, and the conservative measures the decline of authority, and both call the end-result totalitarianism. The liberal's arrival at this conclusion is obvious, and the conservative is concerned with the power vacuum left by the loss of legitimate authority. Into it, he says, moves totalitarianism, which never even made a pretense to wanting the active approval of the masses. Modern revolutions can be seen as an attempt to re-create the experience of foundation by starting afresh, and this seems to be the only defensive mechanism our tradition contains.