First of all, I want to apologise for my long silence. It is partly from being busy with one thing or another, and partly because the post I'm currently preparing has turned out to be even longer than usual. Some writers have the gift of being concise. Unfortunately, I'm not among them.

Anyway, a quick note to bide the time. Today was the wedding between Prince Harry of Windsor and the actress Megan Markle. It has been impossible to avoid here in the UK, and my wife was determined to watch the ceremony. I didn't. I prefer the idea of a non-political monarch to an elected president. Having to choose between Theresa May and Jeremy Corbyn as prime minister is bad enough: if I also had to elect either Tony Blair or David Cameroon (for example) as head of state, I think that I would go mad. The Conservative and Labour parties between them have far too much power as it is (and I am only picking on these because they are the dominant two; I would say the same about any others that reached their level of dominance). And I respect the Royal family for the great deal of good work they do. But I just don't have much interest in the private affairs of the Royal Family, just as I am sure they don't have much interest in mine. Besides, I had things that needed doing in the garden. Despite this, I heard some of the service through the window, and that's what sparked this rant.

Firstly, I want to wish the couple all the best. Being married is not easy, and they know that: they just have to look at their own parents. I hope that their relationship is one of those that endure. I also hope that they can use it to bring happiness to themselves. And I hope that they can use their influence so that, as one team, they can give voice and aid to the numerous voiceless people whom Diana and her sons have always sought out to highlight their forgotten plights.

It's obvious that the couple have a great deal of romantic affection for each other, and that's good. But is it enough?

And that brings me to the sermon, by Michael Curry, Presiding Bishop of the Episcopal Church, (formally Episcopal Church of the United States, but I believe that they decided to shed the United States bit a few years ago). Now, I would warn the reader in advance, that although I am an Anglican, and thus officially I am in a state of communion with him and his Church, unofficially my beliefs are much closer to those of the Bishop of Rome, even though I am as Protestant as they come -- as you would have guessed from my calling him the Bishop of Rome rather than Pope (why concede one of the main points of dispute between us before I the discussion starts?), and the current Bishop of Rome is nowhere near the quality of his predecessors. And I would have to say that the Presiding Bishop is an excellent speaker. Some people have the gift of speaking well. I'm not one of them (in fact, the exact opposite), which, perhaps, allows me to appreciate the gift even more. But, unfortunately, when they go wrong, that makes effective speakers even more dangerous.

The sermon was a marriage sermon, and thus the topic in hand was "love." Of course one never expects great theological insights in a short marriage sermon; you don't have time to go into depth, and it's not the place to do so. But, on the other hand, he is speaking to perhaps one hundred million people about one of the most important topics in Christianity. It is a great opportunity.

And he didn't entirely miss that opportunity. He did reference a few key scriptures; he did well emphasise the power of Christian love to change the world. And Christian love has changed the world, whether on a large scale as in the abolition of slavery, both in the middle ages and then in the eighteenth and nineteenth centuries, or through missionaries opening small schools or clinics which only a handful of people ever hear about, but which are still love in action, or even those who once a week help their elderly neighbours or at the local food bank.

So my point of discomfort is not that he didn't speak about Christian love, but that he didn't clearly distinguish between the Christian vision of love, which can change the world, and the secular vision of love, which most of his congregation would already know about very well. Western secular society is ultimately derived from Christianity, and originally took many of its values from Christianity. One of its great failings is that it has forgotten that, especially when dealing with other cultures such as in the Orient and Middle East, where it finds that what seems obvious to us is alien to them; and what seems obvious to them is alien to us. Because we accept these values without their foundation, we wrongly assume that no foundation is necessary; that their worth is self-evident to everyone. We forget about how revolutionary Christian love was when it first emerged on the scene. And we forget that not everybody means the same thing when they hear the same word.

Tolerance, equality, love, all of these things were inherited from the modern world's Christian ancestor. But the modern world swept aside the foundation behind those virtues. Without a foundation they can shift and diminish. Discussions become more superficial. Understanding diminishes, and becomes more a reflection of what is fashionable than what is true. Secular love can change the world, but not as effectively change it for the better as its ancestor. It's not as though the secular world (at least in the West) doesn't value the concept; more that it doesn't value it enough because modern discussions on many topics including this one, having been divorced from their historical and Christian roots, tend to only be superficial and sentimental. They lack the power of the real thing. And what worried me about the sermon was that the preacher seemed to be speaking only of the secular vision of love rather than drilling deeper and reaching the Christian one.

As I was listening through the window, I could only think "Here is another person who doesn't know the difference between eros and agape." The two Greek words are both traditionally translated into English as "love", but they are, in certain respects, very different in meaning. Eros is the romantic affection that Harry and Megan share. It is a fantastic, and powerful experience. Once you catch the bug, it feels like it will last forever. But it doesn't. If you are lucky, you will get two or three years in that initial burst. If you make it the only foundation of your marriage, then your marriage will fail. You can only hope that in that two to three year window, it will be joined by agape.

Agape is the desire for goodness in general. When directed towards someone, it is to desire good for that person. Eros without agape is useless. It is worse than useless; it is dangerous, since it can blind us into making hideously wrong decisions that can lead to our destruction. Just ask the people of Troy. To understand agape, one thus first needs to understand goodness. To be good is to be fit to fulfil one's natural tendencies or purposes. For a married couple, those include the natural purposes of marriage (which ultimately arise from the institution's role in enabling us to fulfil our natural purposes related to the reproduction and raising of children, as well as marriage's reflection of the internal nature of God and God's relationship with Man). It is agape which leads the husband to take joy in the health and happiness of his wife, and to provide, protect her and help her achieve her intellectual and biological ends; and the same for the wife for the husband. And part of the goodness of the spouse are the goods related to marriage; so in the marriage based on agape each partner seeks above all else to see these satisfied for the other person.

I was only half listening to the service, so I'm not sure which liturgy they used, but the old one says it best.

Dearly beloved, we are gathered together here in the sight of God, and in the face of this Congregation, to join together this man and this woman in holy Matrimony; which is an honourable estate, instituted of God in the time of man's innocency, signifying unto us the mystical union that is betwixt Christ and his Church; which holy estate Christ adorned and beautified with his presence, and first miracle that he wrought, in Cana of Galilee; and is commended of Saint Paul to be honourable among all men: and therefore is not by any to be enterprised, nor taken in hand, unadvisedly, lightly, or wantonly, to satisfy men's carnal lusts and appetites, like brute beasts that have no understanding; but reverently, discreetly, advisedly, soberly, and in the fear of God; duly considering the causes for which Matrimony was ordained.

• First, It was ordained for the procreation of children, to be brought up in the fear and nurture of the Lord, and to the praise of his holy Name.
• Secondly, It was ordained for a remedy against sin, and to avoid fornication; that such persons as have not the gift of continency might marry, and keep themselves undefiled members of Christ's body.
• Thirdly, It was ordained for the mutual society, help, and comfort, that the one ought to have of the other, both in prosperity and adversity.

Agape is not a matter of the emotions, like eros, but of the intellect and will. Eros naturally fades in time (although it can and often does regrow later); we need not be guilty if it fails. But if our agape fails, it is through our own choice, weakness or limitations. Agape keeps us going through the rough times in all walks of life, not just married life, and keeps us on course until things calm down and eros can rise again. It is not eros that keeps a married couple together through all the arguments and rows and disagreements, but agape. It is agape which can revive the dying embers of eros, and make the couple start afresh again. Eros giving rise to some imitation of agape is nothing. Eros rising from a genuine agape is everything.

And that was the problem with the Presiding Bishop's sermon. He mixed up eros and agape. When he first spoke of love, he made it clear that he meant the romantic affection which Harry and Megan shared.

Now the power of love is demonstrated by the fact that we're all here. Two young people fell in love, and we all showed up.

That's eros. But then, he went on to cite the two great commandments, Jesus' sacrifice, and more.

When love is the way, then no child will go to bed hungry in this world ever again.

When love is the way, we will let justice roll down like a mighty stream and righteousness like an ever-flowing brook.

When love is the way, poverty will become history. When love is the way, the earth will be a sanctuary.

When love is the way, we will lay down our swords and shields, down by the riverside, to study war no more.

When love is the way, there's plenty good room - plenty good room - for all of God's children.

Because when love is the way, we actually treat each other, well … like we are actually family.

When love is the way, we know that God is the source of us all, and we are brothers and sisters, children of God.

That's not eros. That's agape. He has shifted the topic, without alerting his listeners. (I'll skip over the common error that we are not all children of God, but only become adopted as children upon acceptance of Jesus, see John 1:12; Romans 8:14-15, and every other reference to us as children of God except when Paul is citing pagan sources as a hook for his Greek audience; or discuss how he plans to encourage the people he needs to reach to sign up to his vision; or change the behaviour of those who nod in agreement and then by their actions make things worse because they don't understand either goodness or human, political and economic reality). So what the bishop was implying is that if you have eros, then agape will come along with it automatically. That they are the same thing. That will either lead people into delusion, perhaps thinking that because agape is the highest virtue, then all forms of eros are equally good and if we "love" then it must be good; or that they don't have to put in the effort and hard work to reform their characters (although it would be better to say have their characters reformed, because its not something we can do by ourselves) to develop true agape because they have eros; or to distract them from delving deeper into what it means to be good; or to think that eros alone is good enough and the point of marriage (so when the eros fades, then so does the marriage); or that romantic fluffiness is all we need and all God wants from us; or that when they see that eros won't change the world (which it can't) they will become disillusioned and give up on agape as well; and a host of other mistakes.

The Bishop's sermon was nice, quotable, sentimentally appealing, especially to the modern West, and utterly devoid of any challenge. It will get rave reviews in the secular media, chattering classes, and even many in the church will lap it up. It's just the sort of thing they like: long on beautiful idealistic utopian dreams; short on the grit, grime, coherence and complications of reality. But neither it, nor the type of love he spoke of will change the world. The world knows all about eros already; it doesn't need to hear any more. But it doesn't know about agape. The Bishop had a great opportunity to tell them about it, and the distinction between these two concepts which share the same English word love. He missed it. In fact, by implying that eros will bring an end to poverty and make us all see each others as brother and sister, when we all know it won't, I think that he made things worse.