Doesn't seem to be necessary since there are nations with perfectly fine internal cohesion without monarchy. Furthermore, national unity in monarchies is identified with the monarch only because he is present already. No country would say "we need more national unity, let's install a monarchy". So it's only an appeal to tradition again.
You might construe this as an appeal to tradition. But if so, it is not blameworthy one. Appeals to tradition are bad if they take the form 'X is traditional, therefore X is good'. This is because, this proposition is usually false. One cannot re-construct my argument in this form.
One could re-construct my argument as 'That X is traditional means X is uniquely suited for certain valuable uses, because these uses are valuable X is good'. The fact Britain has a traditionally has a monarchy means it can take advantage of monarchy in the ways I have enunciated. You are correct to say that a newly installed monarchy would (probably) not yield the same advantages. That is because the monarchy, through tradition, is perceived as having certain legitimacy in the roles it does perform. This relies on a proposition about tradition, but it is not one we can really deny. It relies on the belief that people
do care about tradition; they think about traditional things in a different way to their thoughts on novel things. The tradition of monarchy can leverage this into useful practical application.
On your other point, that monarchy is not necessary for national unity because there are nations with perfectly fine national cohesion without monarchy, fails to touch my argument. I am not claiming that monarchy is necessary for a given level of national cohesion. I am claiming that, in nations were monarchy is publicly acceptable (often due to their historical presence), it is causally efficacious; it increases the probability of national cohesion and perhaps the level of said cohesion. That cohesive countries exist without monarchies does not falsify this claim.
Granted in case of the commonwealth. I don't see how a monarch needs to be necessarily better as a diplomat, though.
In parallel to the previous argument, one reason the monarchy entails special diplomatic advantages is that people care about the monarchy. For instance, tens of millions of people in foreign countries, for whatever reason, watched the royal wedding. This kind of thing gives royal visits a status and prestige unattainable to normal diplomats. This does not mean the royals are any good at the negotiations involved diplomatic work, but they can help build congenial relations with foreign
peoples. This, especially in democracies, is not an insignificant benefit.
That depends on the political powers you give your head of state. What would change if his powers are exactly the same as a hereditary head of state?
The head of state would have some popular legitimacy. This means there would be scope for the head of state to wield whatever power they had. In the UK, the head of state has a long list of royal prerogatives, from choosing who forms the next government to dissolving Parliament to declaring war to promulgating law. Some of these prerogatives could be transferred fairly easy to the Prime Minister but some (for instance, the first I listed) would be impossible to so transfer. This leaves a head of state with some constitutional power and electoral legitimacy. Combined, this gives them some scope to exercise that power.
Good response, thank you! (And I'll make it clear that I'm not arguing any particular case- my own politics aren't liberal, so I've no investment one way or the other- but just trying to improve my understanding.) However, I do wonder if it's possible to distinguish egalitarianism from liberalism as being something concerned by definition with material outcomes. Aren't there some shades of opinion in between the two, which begin with egalitarian principles without coming to communistic outcomes? ("Men are born and remain free and equal in rights. Social distinctions may be founded only upon the general good" as the first article of the Rights of Man and Citizen has it.) So it seems that even if liberalism does not necessarily produce, a contradiction with monarchy, that some interpretations of it will do so. Does that change things at all, or would that simply be another case of ideology-over-practice?
We could issue some interpretations of liberalism that would do so, sure. But there is a danger of playing semantic games here; we can label vastly different theories with the same word. This is conceptually confusing and does not help us understand anything about our principles or society.
As it happens, the liberalism on which liberal democracies are founded is more-or-less classical liberalism. Other popular liberal theories, Rawlsian liberalism for instance, came after the establishment of many such regimes. As I have argued, classical liberalism is certainly compatible with constitutional monarchy.
Whether other 'liberalisms' are compatible with monarchy depends exactly on the type of liberalism. Rawlsian liberalism almost would but not quite; if we dropped the criteria that '
all public offices must be open to everyone with equality of opportunity' it would. Indeed, such considerations are why I am going to some lengths to argue that monarchy can be beneficial; that means we can plausibly say it satisfied the difference principle (that social arrangements should benefit even the worse off) or something like it. Again, whether constitutional monarchy is compatible with other philosophies we might characterize as liberal depends on the precise philosophy in question. Incidentally, I do not think the incompatibility of monarchy with Rawlsian liberalism is a powerful indictment of monarchy; Rawlsian liberalism is false.