This is from The Everlasting Man. My emphases of his text in boldface; my comments in italics. He is speaking here on the view of Marriage as presented by Our Lord (see Mat. 19)
What he [Jesus] advancedwas something quite different; something very difficult; but somethingno more difficult now than it was then. When, for instance, Mahomet madehis polygamous compromise we may reasonably say that it was conditionedby a polygamous society. When he allowed a man four wives he was reallydoing something suited to the circumstances, which might have been lesssuited to other circumstances. Nobody will pretend that the four wiveswere like the four winds, something seemingly a part of the order ofnature; nobody will say that the figure four was written for ever instars upon the sky.
[Chesterton is implying here that Christ is asserting that the nature of Christian Marriage is "part of the order of nature", a fidelity that is somehow "for ever written in the stars upon the sky" in the way no worldly compromise could be.]
But neither will anyone say that the figure four isan inconceivable ideal; that it is beyond the power of the mind of manto count up to four; or to count the number of his wives and see whetherit amounts to four.
[Chesterton is using humor here to illustrate a point. "The Islamic view of Marriage is an impossible ideal for me! How on earth am I to count my wives and assure myself that I have only four? It can't be done!"]
It is a practical compromise carrying with it thecharacter of a particular society.
[This is Chesterton's point. Mohammed's compromise on marriage was a compromise with the Middle Eastern pagan society and culture of his day. Christ's teaching on Marriage - and therefore the Church's - is no compromise at all, and certainly not a compromise with the world or the world's "compromised" attitude toward love, matrimony and fidelity.]
If Mahomet had been born in Acton inthe nineteenth century, we may well doubt whether he would instantlyhave filled that suburb with harems of four wives apiece. As he was bornin Arabia in the sixth century, he did in his conjugal arrangementssuggest the conditions of Arabia in the sixth century. But Christ in hisview of marriage does not in the least suggest the conditions ofPalestine of the first century. He does not suggest anything at all,except the sacramental view of marriage as developed long afterwards bythe Catholic Church.
[Christ taught something in the Gospels that was only fully expressed later. His teaching on Marriage is radically unworldly and new, and not the least conditioned by the world around him - either the Roman attitude toward Marriage or the Jewish. It was a new thing, a suddenly and startlingly right thing - and insisting on it was one of the reasons people were furious with Him.]
It was quite as difficult for people then as forpeople now. It was much more puzzling to people then than to people now.Jews and Romans and Greeks did not believe, and did not even understandenough to disbelieve, the mystical idea that the man and the woman hadbecome one sacramental substance.
[It is this central teaching of Jesus on Marriage that the Catholic Church has always defended, with true mercy and not a parody of mercy - mercy for those abandoned by their spouses and mercy for the broken children of broken families, as well as mercy for those who do the breaking and who repent of it. The worldly pressure to compromise or abandon this teaching today is enormous and it has infested the Church at every level. But of all the Catholic doctrines based on the teachings of Christ, this is perhaps the one with the most Scriptural support. When it comes to Marriage, Pope Francis in his apostolic exhortation and elsewhere refuses to clarify; Jesus in the Gospel refuses to be vague. If the Catholic Church folds on "the mystical idea that the man and the woman become one sacramental substance", or that rejecting this idea by an ongoing sin throws the sinner out of full communion with Christ, the Church will have folded indeed. If the Bride of Christ abandons Marriage she will have abandoned the bridegroom Himself.]
We may think it an incredible orimpossible ideal; but we cannot think it any more incredible orimpossible than they would have thought it. In other words, whateverelse is true, it is not true that the controversy has been altered bytime. Whatever else is true, it is emphatically not true that the ideasof Jesus of Nazareth were suitable to his time, but are no longersuitable to our time. Exactly how suitable they were to his time isperhaps suggested in the end of his story.