Kingdom and realm; an interesting question which demonstrates that language does not just operate under mechanical rules - although such are absolutely necessary - but that language is a living thing which grows, develops, adapts and matures. My Oxford Dictionary of English [2nd Ed 2006] gives ‘kingdom’ - a realm associated with, or regarded as being under, the control of a particular person or thing; and ‘realm’ - a kingdom, as in ‘the defence of the realm’.
The GloWbE, Global Web-based English, one of the corpora which catalogue English usage, returns 87,093 results for kingdom and 24,163 for realm which is an indication, at the very least, that both words are well used but one has a preponderance.
Whatever value and weight the generality of persons may, or may not, give to the Authorised Version of the Bible, the so-called King James Version, it is nevertheless a truth that this book had a massive influence over the development of the English language, in several major countries of the world, for a period of almost three hundred years, from 1611 until, decreasingly, 1888 and thereafter.
So it was to that reference book that I went, immediately, to research the question, and since the words ‘kingdom of heaven’ had been already mentioned I checked those in Young’s Analytical Concordance. I will not go into all the details, they are readily available, but one text stood out like a pinnacle which, in its twin peaks, revealed, to me, something that was fundamental to the understanding of the words and their historical use in the English language.
Ezra 7:23 Whatsoever is commanded by the God of heaven, let it be done diligently, for why should there be wrath against the realm of the king ?
These are the English words, chosen by Englishmen in 1611, to convey the concept ‘realm’ . The word is maleku, which, in this place is actually a Chaldee word but can be considered as Hebrew. It is usually translated ‘kingdom’, very occasionally ‘realm’ - but here, in particular, the translators chose ‘realm’.
The words are uttered, in 455 BC, in the twentieth year of his reign, by Artaxerxes, the King of Persia - then the king of the whole known world (who would, later, be ousted by Alexander the Great) to Ezra the scribe - and these words clearly show that a king of such an empire, accepted that his place was on earth, and that he was subject to whom he chooses to call ‘The God of heaven’.
And in 1611 the translators, appointed by King James the first (in Scotland we recognise him as the sixth), chose to translate the word maleku by ‘realm’ not ‘kingdom’. It’s only a kingdom if God accepts that it is - and that acceptance, at that time, was in doubt. Yes, there is territory; yes, there are people on it; yes, they have property there. But it’s only a real kingdom if God is above it.
Here we see demonstrated the psychology of human beings over a period of two thousand years; a disposition of mind that had not changed for two millenia, for the King James translators accept the deference of Artaxerxes to the God of heaven and they call his kingdom - a realm.
Compared to the God of heaven, who had established another kind of rule on earth than his, Artaxerxes accepts an inferior place. What he had was a ‘realm’ on earth, over men, temporarily. Yes, in other contexts it was a kingdom, and the translators so translate the Chaldee or Hebrew words. But here - in one small text of scripture - is demonstrated what would take me several pages to argue, otherwise.
The ‘defence of the realm’ is a matter of a nation on earth defending territory from another nation. It is about an area of land upon which persons dwell, hopefully peaceably. Humans dwell there. And livestock. But the psychology which predominated upon the planet for two millenia, at least, saw more than that. It saw much, much more. And the difference between ‘realm’ and ‘kingdom’, I believe, ably demonstrates that fact in Ezra 7:23.