‘You tell me of degrees of perfection to which human nature is capable of arriving,’ Abigail Adams wrote to her husband in 1775, ‘and I believe it, but at the same time lament that our admiration should arise from the scarcity of the instances.’ John Adams was in Philadelphia, arguing with other representatives from the American colonies about whether to break away from Britain’s empire and form a new kind of government. From their home in the Massachusetts countryside, Abigail bombarded him with cautionary questions. If you set up a democracy, ‘will not ten thousand difficulties arise in the formation of it?’

Dreams of human perfectibility are as old as recorded thought. Ancient scriptures and poetry grapple with questions about how far any human being can resemble or rival the gods, whose beauty, knowledge, and power to control human lives far surpass any mortal’s. Heroes were humans whose strivings brought them close to divine perfection; ordinary folk were encouraged to admire and emulate them – but not too boldly. While the quest for flawlessness inspires great feats of mind and action, the ancient Greeks knew it could get perfection-seekers into trouble.

There is an element of risk, even recklessness, in Heracles’ or Theseus’ extraordinary feats. Ancient heroes were always on the brink of hubris – prone to overestimate their own powers, forgetting they were merely human or, at most, demigods. Acts of hubris usually involve a fatal mistake: imagining that your power goes hand in hand with wisdom, or that might makes right. The historian Thucydides shows how far his own city, Athens, had succumbed to collective hubris when its ambassadors tell the conquered Melians that ‘right is only in question between equals in power; the strong do what they can and the weak suffer what they must.’ Overrating their power, their wisdom, and their virtue, the Athenians go a step too far when they try to conquer Sicily – and fail most dismally.

But though warnings against optimistic overreaching run deep in many traditions, not just western ones, humans keep finding excuses to cast caution to the winds. Modern ideas of progress extend hopes of ever-increasing perfection from individual heroes and imperial cities to all humanity – or at least some part of it that can enlighten and civilise the rest. Rooted in religious notions of providence as well as in the astonishing scientific breakthroughs of the past several centuries, progressive optimists believe that humanity – or parts of it – is on an ultimately irreversible path toward becoming more intelligent, efficient, fair-minded, capable of controlling its natural environment. ‘The Idea of Progress,’ wrote the historian J.B. Bury in 1920, was at that time ‘the animating and controlling idea of western civilisation … The ideals of liberty and democracy, which have their own ancient and independent justifications have sought new strength by attaching themselves to Progress.’

But does the value of liberty and democracy depend on how far they elevate the intelligence and moral character of humanity? That might make sense if we could all agree on what constitutes intelligence and moral virtue, and how they should and should not be advanced. Yet the combined lessons of history and philosophy suggest that such agreement will never come about, unless some new technology reconfigures our brains to resemble those of robots, not humans.

Perhaps democracy and liberty should not be judged by any progressive telos – by how far they promote some noble but controversial set of goals – at all. They should be valued instead and in so far as they defend what makes people different from machines: their freedom to choose their own goals and deliberate them on an equal basis with others. Freedom and democracy should come first, particular ideals of progress a very clear second. Otherwise progress takes over and says: ‘No true freedom or true democracy can exist until we have overthrown whatever state of affairs we find oppressive.’ The more modest kinds of freedom and democracy I’ve just mentioned are usually the first casualties of such crusades, whether they come from the left or right, or claim the moderate-sounding name ‘liberal.’

The ancient Greeks and Romans understood that if you want to construct a lasting government you need start with human beings as they are, and not as you wish to make them. They never stopped insisting that however enlightened or powerful any government gets, however intelligently designed, it will always have to do daily battle with impulsions that gnaw away at it from within: people’s demands for boundless personal freedom; desires to stand higher than others and dictate terms to them; overconfidence about their own rightness and righteousness; and attractions to authoritarian leaders.

Prudent lawmakers should ‘presuppose that men are bad’ while devising laws to ‘make them good,’ declared Niccolò Machiavelli in his Discourses, echoing ancient wisdom. His point was neither a cynical pessimist’s nor a progressive optimist’s one. The laws only put a check on people’s impulses to act ‘badly’; they cannot eliminate those impulses altogether, in individuals or cities or humanity as a whole. Still, if you design your democracies for citizens who are not essentially good, yet capable of reining in their own ‘badness’, you have a better chance of crafting institutions that limit bad behaviour and coax out the better.

That, contra more ambitious progressivists and perfectionists, may be the best we can do. It is not so bad. Some might even say that when it works, even now and then, that is something to celebrate in a spirit of very cautious optimism, inspiring us to work harder every day – never trusting that progress, like some unstoppable cosmic machine, will do the work for us.