The six basic principles of responsible government don’t, by themselves, converge on a single system. Instead, it’s best to first look at those regimes they entirely eliminate.
Necessity
Egalitarianism is, in essence, a lack of organized government. Anarchy is a repudiation of it. Neither is well-suited to the needs of a large, diverse state. Human nature is to be social, and that means forming relationships, whether romantic, platonic, friendly, or simply on the basis of mutual acquaintance. Those relationships can easily turn into alliances, recognitions of shared purpose. From there, it is a short step to self-organization, and then to government. Therefore, anarchy can never be more than merely a temporary state.
Purpose
A government that does not protect the lives of its citizens is a failure. One that does not uphold those citizens’ rights is equally lacking, though the nature and quantity of those rights can be argued. It is clear, however, that some systems of rule are entirely unsuitable. Those predicated on the absence of individuality—Leninist communism, for instance—cannot be considered acceptable for governing a free people. Likewise, those which ignore fundamental human rights—theocracies being only the most familiar example—must not be seen as viable. But even democracy is not infallible, as the tyranny of the majority can be used to strip rights from the minority. Good government, in this sense, is far more than a question of who rules. It also must take into account how those who rule protect those who do not.
Evolution
Nothing in this world is without change, and that includes society. Social mores shift over generations, but a rigid government can fail because it fails to adapt to these seismic shifts. To prevent this, a state must give some allowance to the possibility of radical changes to its structure, to its core tenets. Those that do not, those that remain fixed, are doomed to fall. Again, theocracy, with its strict insistence on dogma and received wisdom, is the perfect illustration. But a theocracy can adapt by reading and interpreting its scriptures in a new light, while a strongly segmented, highly conservative aristocracy may instead resist the natural evolution of culture, leading to failure.
Equality
Every human being is unique, but we all share many things in common. It is easy, common, and perfectly natural to separate humanity into groups based on the presence or absence of a specific factor. However, to institutionalize this separation is to create an imbalance between members of a preferred class and outsiders. Implementing this sort of segregation by intrinsic factors, those we are physically, mentally, or psychologically unable to change, sorts humanity into those who are—by definition—haves and have-nots. This leaves a segment of the population without political power, without the opportunity for redress, and that segment will only seek to find a new outlet for such. Legislative tribalism, in the form of laws motivated by race, religion, sex, or other factors, is a failure of a government to protect (as by the Principle of Purpose) a certain portion of its citizenry. Executive tribalism, as seen in caste systems, aristocracies, communism, and oligarchy, bars this same portion from using its political voice.
Cooperation
Once again, we return to egalitarianism, as it is a prime example of the nature of competition. When every man is for himself, he can accomplish only what is within his own means. A larger conglomeration, however, can achieve greater things. This is because of resource pooling, specialization, and leadership, among other factors, and it is an expected consequence of our social nature. The most striking examples are those grand projects requiring the cooperation of an entire state, but this sort of socialism is inherent in any system of government. That does not require a surrender of all free will, as in Hobbes’ Leviathan, nor is it a condemnation of capitalism. When we accept the role of government, we commit a portion of ourselves to it, hoping that we receive greater benefits in return. It is this equation, in its lack of balance, where the failure of neoliberal technocracy lies. Yet there is equal imbalance in pure objectivism and pure collectivism.
Initial Conditions
The final principle is the most culture-specific, and it is here that one government system—or the idealized notion thereof—is singled out. However, the Constitution itself does not uphold all the ideals stated above. In its original form, it embraced inequality. It made little space for grand-scale cooperation. In accordance with the Principle of Evolution, however, it has changed to reflect the times, the changing beliefs of those it represents. Other founding documents fail a different set of fundamental principles, and in differing ways. They may be suitable as a starting point for deriving a system of government, but few begin so close to the ideal. Wholly unusable, by contrast, are scriptural resources such as the Ten Commandments, as these are defined by their violation of the Principle of Equality.
None of this is to say that these forms of government are invalid. If a people chooses to create for itself a state based on a violation of the Principles, the choice is theirs alone, and it is not for us to assign fault or blame. Those regimes, however, may not endure.