Jesus (or the scribe) appears to be quoting from the Old Testament, but one phrase does not exist in any text of the Commandments: that we should love the Lord our God with all our mind.

  It is easy not to notice this phrase, and indeed Matthew, Mark and Luke don’t notice it. We know this because normally when Jesus departs from the Old Testament it is noticed, and remarked upon, and made the subject of a whole “But I say to you…” discourse.

  Not here.

  There are two aspects to this. One is what it says about the past, the other is what it says to us. The past is straightforward. The Jews have never been “people of the Book” in the sense of believing in the Bible and nothing but the Bible. They have, it is true, had a peculiar reverence for every sacred word, but they have lived not in unthinking obedience to those words alone but in a dialogue, you might even say in a relationship, with the sacred text. So the fact that “all your mind” appears here, without attracting notice or comment, must mean that it had become a part of the generally accepted interpretation of the words of Scripture. When, centuries after the Pentateuch, the Jews came across the new, Greek ways of thinking – as the Wisdom literature shows that they did – they immediately realised that this new thing called “mind” was included, no doubt about it, in the commandment to love.

  What this says to us is more important than just a footnote in the history of ideas. It is the foundation and justification of all science. God does not command the impossible. If he is to be loved with the mind, that can only be because he is lovable with the mind, or, to detheologize the language, because Ultimate Being can be related to rationally. The Gospel phrase tells us that things make sense and that we have the equipment to make sense of them.

  What does omnipotence mean? Does it mean that the Omnipotent can do anything at all? If that were true, all science would be at an end. If God willed that when I dropped a glass on the floor it would shatter, then even if God had willed the same whenever anyone in the past had ever dropped a glass, that would still not bind God. God would still be free to decide, if I dropped a glass on the floor now, that this particular glass, alone among all the glasses in history, should bounce and not break.

  Which is to say: on this interpretation of divine omnipotence, science is impossible. We cannot predict the result of an experiment, because next time God may decide differently. We cannot even lay down laws of nature based on previous experience, because to call a law a “law” is to claim to be able to bind God, which is blasphemy.

  This is not merely an academic quibble. When the 11th-century Muslim philosopher al-Ghazāli propounded this very idea, it captured the mainstream of Islamic thinking and led to the virtual suicide of science in Islam and the abandonment of rational thinking about the physical world, as being unnecessary, or sacrilegious, or both.

  We are saved from this by this one little phrase in the Gospel, about loving God with all our mind. It is more than mere permission, it is a command to understand, to go out and do science, and it was followed whenever Christians had leisure to think. It led to the dazzling 13th-century renaissance and the birth of modern science, and we are still living through its consequences.

  As for divine omnipotence, this is not the place to go into it in detail, but the answer to al-Ghazāli must surely be that God can indeed make the glass bounce, but God cannot make the glass bounce and still be God, since to break the laws and regularities of nature whimsically and without reason would be to abandon lovability-with-the-mind. This is exactly the argument that theologians use against pointless or frivolous miracles, but it applies to science as well, and to the possibility of doing science at all.

  The other great controversy of the time, which took more than a century to settle, was on the nature of grace. At one extreme was Pelagianism, named after Pelagius, a British monk (who held at least some form of it): this made justification something we could achieve for ourselves. If you take that argument far enough, there seems little room for the grace of God. At the other extreme was what might be called Augustinism, a selective view of St Augustine’s counter to Pelagianism, according to which all that is good comes from God and we, of ourselves, can achieve nothing good at all. Now, if you take that particular argument far enough, God has already decided whether we are saved or not, and nothing we can do can have any effect on it, so that there is no point in performing good works or avoiding sin.

  Current opinion is that in striking the balance between these extremes Vincent himself was what would now be called a “semi-Pelagian”, semi-Pelagianism being a kind of half-way doctrine which was formulated in southern Gaul in the early fifth century and formally condemned in 529 at the Second Council of Orange. It was only in the 17th century that this particular label was applied to Vincent, and in any case the presence or absence of such a label does not detract from the value of everything that Vincent taught and wrote. The branding of one’s doctrinal opponents as being in every sense depraved and unclean is a characteristic of only certain historical periods – admittedly, including the 21st century. Vincent’s own analysis of the development of doctrine brings good sense into an area where it is much needed, and this is why this reading has been chosen for the Liturgy of the Hours.

  In the earliest centuries all vestments were white – the white of baptismal purity and of the robes worn by the armies of the redeemed in the Apocalypse, washed white in the blood of the Lamb. As the Church grew secure enough to be able to plan her liturgy, she began to use colour so that our sense of sight could deepen our experience of the mysteries of salvation, just as incense recruits our sense of smell and music that of hearing. Over the centuries various schemes of colour for feasts and seasons were worked out, and it is only as late as the 19th century that they were harmonized into their present form.