Consider two moments in the history of Western civilisation. The first, from the late 15th century, concerns one of the moving spirits of the Italian Renaissance, Pico della Mirandola. Born into an aristocratic family, he was a child prodigy, mastering Latin and Greek at an early age. Initially intending a career in the Church he went to the University of Bologna to study law, but widened his interests to include philosophy, which he pursued at the universities of Ferrara and Padua.

In 1486 he completed his monumental 900 Theses on the entire range of human knowledge. To accompany them he wrote his Oration on the Dignity of Man, one of the masterpieces of Renaissance humanism. In it he argued that the human person was the centrepiece of creation, the only being other than God Himself who was endowed with freedom.

This is how he imagines God addressing the first human: “We have placed you at the world's centre so that you may survey everything else in the world. We have made you neither of heavenly nor of earthly stuff, neither mortal nor immortal, so that with free choice and dignity, you may fashion yourself into whatever form you choose. To you is granted the

power of degrading yourself into the lower forms of life, the beasts, and to you is granted the power, contained in your intellect and judgment, to be reborn into the higher forms, the divine.”

Five hundred years later a quite different statement about the nature and dignity of humankind appeared. Published in 1997 by members of the International Academy of Humanism, its signatories included distinguished scientists, philosophers and novelists. The subject at hand was the permissibility or otherwise of research into human cloning. The signatories all supported such research, and explained why.

“As far as the scientific enterprise can determine, Homo sapiens is a member of the animal kingdom. Human capabilities appear to differ in degree, not in kind, from those found among the higher animals. Humankind's rich repertoire of thoughts, feelings, aspirations and hopes seems to arise from electrochemical brain processes, not from an immaterial soul that operates in ways no instrument can discover.”

On this view, the human person is not distinctive at all. We are part of nature; nothing more. There is nothing corresponding to the soul, nor is there anything in the “rich repertoire” of works of the human spirit to differentiate us in kind from other forms of life. Our hopes, dreams and ideals “arise from electrochemical brain processes” - implying that this is all they are.

Quite apart from the genetic fallacy implicit in this statement (we are what we began by being: a butterfly is only a caterpillar, a human being only a naked ape), what is striking is the sheer loss of the sense of grandeur and possibility that drove Renaissance humanism. Reviewing this history of the descent of Man it is hard not to feel that we have lost as well as gained. For what does it profit humanity if it gains the world and loses its soul?

The odd thing is that dignity seems to go hand in hand with humility. Only when people discovered that they were not gods were they able to reach their full stature as human beings. Finding God, humanity found itself. Losing God, it is at risk of losing itself. For the biblical view of the human person - free, responsible, lonely yet capable of redeeming his or her loneliness through the moralisation of love - is what gave Western humanism its singular glory. For once, the human person confronted God in a realm of freedom and was lifted to the heights.

When human beings lose faith in God they lose faith in human beings. They abandon their moral qualms about abortion. Some, like the biologist Francis Crick, have no problem with infanticide. They favour voluntary euthanasia, death on demand. They give their support to eugenics and “designer children”. For what, after all, are we but a random concatenation of genes, a handful of dust?

Faith does not disagree; “From the dust you came and to the dust you will return.” It merely adds one detail. There is within us the breath of God. We have immortal longings. Lose this and we will lose all else. We will have knowledge without wisdom, technology without reticence, choice without conscience, power without restraint.

Rabbi Sir Jonathan Sacks is Chief Rabbi of the United Hebrew Congregations of the Commonwealth