Personally, I would start with a national government run by well-trained and well-behaved philosophers, give it 50-100 years and if that worked out then I might just consider it. And, ideally, it should be a Christian one. I don't think I'd fancy the idea of a worldwide Islamic State to be honest — Apollodorus
Well I agree an Islamic State is a very bad idea and a real threat... I disagree that a government or a society should ever have a singular religion, even if Christianity would be worlds better than Islam... I think an ideal system of government should necessarily disqualify the religious from holding office as political representatives over society. (I try to explain my reasoning below)
I do not believe with any certainty that the religious are not correct in their particular religious belief (though admittedly I doubt that they are)... My personal skepticism towards any religious doctrine(s) is, I believe, irrelevant to this evaluation.
I consider the role of a representative official as a job, much like any other in that there is a prerequisite to a person's qualification which is that they can (and will) do the job. If a job requires that a person must be able to aim and fire a gun and they cannot, though they may have good intentions in applying for the job, they are objectively unable to serve in that capacity...If a person is required to lift over 100 pounds in order to perform the duties of a job and they can't, then they are unable to serve in that capacity. It is not meant to insult or disgrace the applicant, it is just an objective fact.
In society, applicants are screened for their qualifications... Generally, for the most important jobs with the highest stakes, the screening process is more rigorous... there are more qualifications, and the number of people in society who are qualified for the particular position shrinks dramatically...
Furthermore, the screening process of any occupation is not randomly carried out by anonymous people, it is specific and carried out by experts who are familiar with the job being applied for.
So, if more important jobs require more screening, then the most important job should require more screening than any of the others, and a higher bar for qualification... I'd imagine you and I do not disagree that the most important job, in a hypothetical world government, would be the execution and regulation of the government in tandem to those other people with that same job or above all others in the case of an executive like a president.
So what are the qualifications? That is subjective, as it depends on what functions you have assigned to the job of executing the will and/or interests of a society...
These are the main three functions I ascribe to a representative of any society
1st function:
(What should go without saying) To prioritize the job(or the function) above everything else.
----in the most important job in the society, it has never been so important for any job in that society that the person to whom we give the job is devoted to it in an absolutely zealous manner... they must be willing to die rather than to betray their objective... they cannot be selfish, under any circumstances. So, whatever functions we add after this, it is important that we are certain that the first qualification of the person is that they are able, willing, and absolutely determined to carry them out. They must be selfless.
2nd function:
-----To preserve the physical existence of the society over which he or she presides... No ideology of society, no moral injustice or cost to its comfort is so great as to forfeit the physical survival of the society altogether rather than to suffer that cost.
3rd function:
-----Within the limits of the second function, to increase and preserve the liberty and freedom of all the individual members of society... it is only the requirements of the second function that should (and will) limit the 3rd function, such that no one in society will ever have limitless liberty as long as they exist relative to others. We can only increase liberty through higher efficiency and sustainable material growth.
The first three functions here describe the intentions I would require of a person before I would say that it is possible that the person could ever be considered perfectly "qualified" to be a representative of a society. To be a representative of all society, the primary candidates must pass the screening process and come closer than anyone to meeting these first 3 functions
And the rest is a determination of whether they can carry out those intentions... Essentially just education and experience in the duties of a leader over society... Generally, a vast political, economical, historical, ethical, philosophical, and logical education and a proven record of success...
A true follower of religion (or a shared, exclusive doctrinal ideology), is prevented from meeting the first two of my qualifications... given a choice, a true believer will (to the extent they are loyal to their religion) prioritize the spiritual ideology of society over its physical survival, as they believe that their specific ideology will correlate to an eternal, non physical survival after death which they prioritize over the impermanence of physical survival... therefore, should the general physical survival of a society ever become exclusive to the ideology of that person's religion, they will be bound by their loyalty to their religion to abandon the cause of physical survival for "spiritual" survival, which they always thought was more important... the religious tell us this quite often.
I would ask a person applying for representative leadership who is religious this hypothetical question:
"would you prefer that all of your society were physically destroyed tomorrow and everyone went to your version of heaven, or that your society were preserved physically for millions of years and every generation of that society went to your version of hell?"
If they can answer with the second option, then I'd say they are a terrible adherent of their religion and a vicious person but, nonetheless, a potential political candidate. Though I would find them personally dislikable, as (according to their belief) they could only possibly carry out their function (according to this hypothetical) of preserving physical survival as they desired everlasting suffering for everyone to follow...they would be unlikely to carry out the third function...
In any case, even if there are some religious ideologies that could potentially allow a follower to pass the qualifications (if they could prioritize the physical wellbeing of society over an ideology of non physical wellbeing), it is dangerous to pick favorites with religion, because we would could bring about a "world religion" which would be a terrible risk to society should that religion (whatever it may be) evolve over time into a less sustainable form which contradicts the function of a representative official