The Archbishop of Canterbury has delivered a sermon at a Westminster Abbey service to mark the bicentenary of the Slave Trade Abolition Act.
Dr Williams said historic and modern slavery were crimes
Human beings are born free, yet everywhere they are in chains. A great and inspiring slogan for progressive thinking in the last two centuries; but the very fact of this act of commemoration should make us question it.
We are born into a world already scarred by the internationalising and industrialising of slavery in the early modern period, and our human inheritance is shadowed by it.
We who are the heirs of the slave-owning and slave-trading nations of the past have to face the fact that our historic prosperity was built in large part on this atrocity; those who are the heirs of the communities ravaged by the slave trade know very well that much of their present suffering and struggling is the result of centuries of abuse.
It is true that other nations, in the Middle East and South Asia, share something of the same inheritance, similar shadows cast on their history by various sorts of slavery.
The situation of bonded child labour among the lowest castes in India for example remains a painful scandal, crying out for resolution - though the Church's own record in its relations with the caste system is far from straightforward.
Slavery is not a regional problem in the human world; it is hideously persistent in our nations and cultures.
But today it is for us to face our history; the Atlantic trade was our contribution to this universal sinfulness.
Human beings are born into an inheritance of one kind or another, and it is a fiction to speak as though we could be free of this.
Let us speak the truth to our neighbours, for we are members of one another, says St Paul.
One of the strangest aspects of our modern mindset is the assumption that we needn't think truthfully about where we came from, how our cultures and habits were formed, how we collectively got into the nets and tangles that frustrate our best intentions.
Christian thinking has always traced this back to the very first twist in the human consciousness towards selfishness, at the very beginning of human life; it is what we call original sin.
No; we are not born free. But we are born for freedom.
We are born with a task before us.
We are to learn how to be free; and that means to learn how to be free by facing the legacy we inherit without fear, excuse or untruthfulness.
Often, so often, that means asking others to tell us the truth we can't see for ourselves - we ourselves are the 'neighbours' who need to hear the truth, in St Paul's terms.
That is why, in this service, and in the act of repentance and restoration last Saturday, Christians of British descent invited others to join them and to speak to them some of the necessary words of judgement and of mercy.
And our readings today remind us that this task of becoming free by listening for the truth is more than any of us can manage just in our human strength.
We need the Spirit of the Lord upon us and within us.
That Spirit is the Spirit that, in the Bible, hovers over the beginnings of creation, the Spirit that gives strength for the making of beauty and order in the world, the Spirit that descends into the body of Mary to bring to birth the Spirit-filled Jesus of Nazareth, whose life and death and resurrection break through the tangles of inherited guilt and responsibility and unfreedom, the Spirit that creates a community in which each takes responsibility for all as they become 'members of one another'.
What Paul calls 'grieving the Spirit' must therefore include all those aspects of our human behaviour that destroy beauty and order, that unravel the bonds of creation, that seek to block out the good news that there is a God whose purpose is always to set men and women free.
What greater grieving of God's Spirit could there be than slavery?
Whether in the forms that Wilberforce and Clarkson and Equiano denounced or in the forms in which it is still around today, debt slavery and sex-trafficking and forced labour and child abduction and exploitation, it is an offence against the created order of equality, an offence against the dignity of humans as called to share in some measure in God's own creative responsibility, an offence against the interdependence that makes it impossible for any one truly to flourish at the expense of any other person whatsoever.
The Queen joined the 2,000-strong congregation at Westminster Abbey
So have we good news to tell the world today, or only the grim recognition of just how deeply addicted human beings are to inhuman behaviour?
Yes, we have good news; without it, we cannot hope for the transformation of this nation and world, the kind of transformation achieved through the witness of those like Equiano and Wilberforce who woke up the conscience of an entire civilisation.
Yes, because the Spirit of which Jesus speaks in his 'manifesto' in the synagogue at Nazareth is of inexhaustible power and eternal energy, God's own person and act.
Slavery was taken for granted by Christians and non-Christians and irreligious people for centuries if not millennia; humanistic scholars and atheist liberals alike accepted it no less than the majority of religious believers in all faiths.
Yet the Spirit that spoke in Jesus was a Spirit contemporary and alive for those who, two hundred years ago and more, refused to take it for granted because they saw something of the truth about God and about humanity.
Is that Spirit contemporary and alive for us?
If so, we shall indeed have the courage to face the legacies of slavery - the literal degrading slavery of the millions who, then and now, are the victims of the greed of others, and the spiritual slavery of those who oppress and abuse, and so wreck their own humanity as well as that of others.
We shall have the courage to turn to each other and ask how, together, we are to make each other more free and more human.
May that Spirit be upon us and in us in our struggles.