In 2010, I had an epiphany about my personal philosophy that, in my view, reveals all of progressive, liberal, and humanist politics at its most basic and unified essence: Liberty, Equality, Opportunity - a trinity of moral ends-in-themselves that can neither be subdivided nor sustained in practice unless all three are protected and promoted. The conceptual power of "LEO" is that it unifies principles we all generally share, but which we are often at odds to optimally balance, let alone articulate in a way that doesn't simply trap us into dead-ends by the limitations of language. By looking at it this way, we can understand our politics as a three-dimensional system with the "ideal good" being at the intersection of these three qualities, and realize the fact that unless all three are balanced, what results will be both unstable and unsustainable.
Try to imagine a circumstance where any of the three is lacking. What you get is a dystopia where even the values that are promoted in theory are degenerate in practice. For instance...
1. Consider anarchy: Liberty and Equality are technically present, but only in their basest and least constructive forms. When no institution is effective enough to control individual behavior, people are theoretically just as free to do good things as well as bad, but in practice all you get is the latter. Moreover, people are theoretically equal, but only because insecurity and desperation are universal, with even the predators fighting over transient scraps of illusory power. And both perversions are the result of one of the three legs of the LEO tripod being totally nonexistent - Opportunity. No idea, no matter how clever; and no amount of work, no matter how diligent, can be rewarded so long as anarchy persists.
2. Consider fascism: Opportunity is strongly present in a fascist state, at least at first - those with the Will to rule and excel in some profession just smash their way to their objectives, and align themselves with unscrupulous powers who will reward their competence in exchange for obedience. However, it's unstable: Sooner or later the people who smash and murder their way to the top simply become a stifling aristocracy who do everything they can to suppress the same kind of revolutions from toppling them. And in a monstrous, diabolical way, even Equality is present in a fascist state in the form of the "right of conquest" tautology: Everyone is equally entitled to murder and enslave everyone else, and those who do so successfully are "justified" by definition. But Liberty is not permitted on any level: You may not choose to coexist peacefully, or dissent, or take moral positions - fascism forces all parties to a zero-sum test of strength, and you will either join, be conquered, or conquer in turn.
3. Consider communism (or other form of authoritarian egalitarian state): Equality is the single overwhelming value in a communist state, but it is both in a degenerative sense and unstable. The vast majority of people are equally oppressed, deprived, and exploited, but even the benefits of that Faustian bargain are ephemeral because the cunning and unscrupulous learn how to cheat the system, forming black markets and mafias around the bits and pieces of inequity that crop up in a bureaucracy. And, of course, neither Liberty nor Opportunity are present - everything is strictly regimented from the top, and monolithic Leviathan states determine who is worthy of reward rather than any sort of natural, democratic, or fluid process, assuring that ultimately only the people who control the rewards are rewarded and nothing is permitted to change.
These are just the most extreme examples, but you can have any number of intermediate versions, e.g.: The social Darwinian capitalist kleptocracy, where you have Liberty in theory but not practice (because few can afford to do anything other than barely survive), and Opportunity only in the sense of being unrestrained from preying on others, much like fascism; the petty monarchy, where there is no Equality or Opportunity, but a kind of Liberty in the fact that the rulers mostly don't care what you do and won't exert themselves to control it except where their own interests are concerned; and the primitive tribal state, where there is general Equality because social control is extremely simple, but neither Liberty nor Opportunity have meaning because there's little structure against which to either dissent or build upon.
As these examples demonstrate, if you shortchange any of the three, the other two become a sick joke and/or radically short-lived. This is why we find such technically bewildering alliances as the partnership between libertarianism and fascism: Not because they agree on anything specifically, but because they have a mutual enmity toward LEO as a unified system - both oppose the practical, politically-enforced maintenance of Liberty and Equality, preferring that people not be given a choice about participating in zero-sum competitions for power and privilege. The only significant difference is that libertarians prefer that the ruthless wield power through corruption of explicit governments rather than directly wielding them, but this preference is idle at best.
In practice, the two blend smoothly into each other, with libertarianism rapidly degenerating into some other crippled state - anarchy, kleptocracy, monarchy, fascism, or if a radical counter-reaction occurs, an authoritarian egalitarian state like the French revolutionary government or the 20th century Communist dictatorships and oligarchies.
You need Liberty for people to access and exploit Opportunity, and to demand and maintain Equality; you need Equality to maintain Liberty and effectively, robustly distribute Opportunity; and you need Opportunity for Equality and Liberty to efficiently benefit society. These are three words, but in practice they are one, deeply interconnected dynamic system, and trying to turn any one or two of them into the slave of the other(s) creates disfigured, sickly, or stillborn governments and cultures.
This realization was codified into the very fabric of the US government, in the three-branch structure of checks and balances, but as often happens the success of it merely created more advanced opportunities for failure. As a result, the state that was the most robust in modern times at embodying LEO (and second only to the 400-year Roman Republic in all of human history) - mitigating and forestalling the violent revolutions and stagnant vulnerabilities that have destroyed most other governments or left them defenseless against external events - has fallen prey to its own hyper-evolved economy, with financial systems that operate with such speed and complexity that the corporate institutions of the rich constantly outwit and outflank the political system that makes them possible.
The solution to this is not to retreat to greater simplicity, which would be to simply pretend that history never happened or that we don't know what we know: That would be little more rational or constructive than dealing with a personal crisis in adulthood by reverting to adolescence. Nor is the answer to cultishly mimic societies with an equal and opposite imbalance to our own current problems, since - for instance - it obviously hasn't helped more socially-inclined states like those of Europe to avoid the predations of austerity that are wracking most of the continent. The answer is to take the profound understandings embodied in the US Constitution to the next level - to a more evolved, more rapid set of mechanisms that we can rely upon in daily life to regulate and control the otherwise unchecked corporate anarchy/monarchy that rules over us, and stop it from corrupting and obstructing our ability to appeal to slower, more distant political institutions.
The Occupy movement had the right idea in this respect, at least initially, in that it tried to envision what LEO might look like on a granular level that people could interact with in their daily lives, but it lost momentum when it became more concerned with its own treatment by authorities than in creating, communicating, and implementing ideas. Part of it was that a lot of the people at its core were themselves impatient with the reality of a democratic mass-movement whose larger community didn't necessarily care about the laundry-list politics of its most active constituents, and some of whom felt hindered or "co-opted" by mainstream involvement. But nothing stops any of us from building on the foundations of Occupy's early successes and trying to implement a more rigorous, more robust set of democratic mechanisms in everyday life and in our local communities. At the nexus of Liberty, Equality, and Opportunity is a free, humane, and limitless society, if we are smart enough, courageous enough, and yet humble enough to pursue it.