Absolute power does not corrupt absolutely. Power simply allows people to express their true selves. People do not change: they simply emphasize or deemphasize their own nature in order to fulfill other aspects of their nature, which is self-survival, the desire for pleasure, etc. As Glaucon said, people are only just because they cannot be unjust successfully. Therefore, absolute power does not corrupt; it simply allows for the already corrupt to express themselves. Hence, if you can find someone who is not corrupt, then you can have a good monarchy. Moreover, because the intrinsic nature of people is evil, then one must be born good to be a good and just ruler. It has not always been the case that monarchs are tyrants; many true Biblical rulers in the past have ruled well, with one or two mishaps, which is intrinsic to any person. Therefore, because Christians are "born again" into a godly nature, then only a theocratic monarch can reign in modern day. Democracy is still horribly bad. A totally uncorrupted monarch is impossible; however, if one is a true Christian, then one has been born to a new nature of godliness, which will battle with the fleshly desires.