He was a medieval saint, who was reputed to have levitated

and had visions of the Virgin Mary.

He was much concerned with explaining how angels speak and move.

And yet, he continues to matter because he helps us with the problem

which continues to bedevil us:

how we can reconcile religion with science,

and faith with reason.

Aquinas was both a philosopher and a saint.

Refusing either to lose his faith or mindlessly believe,

he developed a new understanding of the place of reason in human life.

Aquinas's monumental contribution was to teach Western Europeans civilisation

that any human being, not just a Christian,

could have access to great truths, whenever they made use of

God's greatest gift to human beings: reason.

Aquinas broke a logjam in Christian thinking -

the question of non-Christians could have both wisdom

and at the same time, no interest in or even knowledge of Jesus.

Aquinas universalised intelligence.

He opened the Christian minds to the insights of all of humanity

from across the ages and the continents.

The modern world, insofar as it insists that good ideas can come from any quarter,

regardless of creed or background, remains hugely in Aquinas' debt.

Thomas Aquinas was born to a noble family in Italy in 1225.

As a young man, he went to study at the University of Naples

and there came into contact with a source of knowledge which had just then been rediscovered -

the texts of ancient Greek and Roman authors.

Aquinas then became an academic at the University of Paris

and an exceptionally prolific writer,

producing nearly 200 pieces about Christian theology

in less than three decades.

His books bear beautiful and strange titles,

like the Summa Theologica,

and Summa Contra Gentiles.

Such was his devotion to knowledge

even at the moment of his death at the age of 49,

Aquinas was reputed to have been in the middle of writing an extended commentary

on the Song of Songs.

After he died, he was canonised in the Catholic church

and he is now the "patron saint of teachers".

Aquinas's starting point was that some of the world's greatest thinkers

have not been Christian,

but this didn't bar them from having huge insights,

because, as Aquinas proposed, the world can be usefully explored

through reasons and not just through faith.

To explain how this could work,

Aquinas brilliantly proposed that universe and all its dynamics

operate according to two kinds of law

For Aquinas, a lot of the world follows natural laws.

We can find out for ourselves how to smelt iron,

build an aqueduct, or organise an economy.

And none of these relies on believing in God.

Aquinas discussed Jesus is in junction to

Jesus may have given this idea a particular memorable formulation,

considered Aquinas,

but it's in fact been a cornerstone of moral principles

in most societies at most times.

How could this be possible?

Well, the reason, Aquinas argued,

is that it's an idea that belongs to natural and not eternal law.

Aquinas considered that in a few situations

God does works simply through eternal law,

outside of human reason.

And he cited prophetic revelations and the visits of angels as examples.

However, he reassured us the most useful knowledge

can be found by atheists and secular-minded people

within the realm of natural law.

Aquinas's ideas unfolded at a time when Islamic culture

was going through very similar dilemmas as Christianity

in terms of how one can reconcile reason and faith.

For a long time the Islamic caliphates in Spain, Morocco and Egypt

had flourished by being open to knowledge from all over the world,

generating a wealth of new scientific ideas and philosophy.

However, due to the increasing influence of fanatical religious leaders,

Islam had become more dogmatic and oppressive by the time Aquinas was born.

It had, for example, reacted violently against the Muslim philosopher Averroes.

Like Aquinas, Averroes's been deeply influenced by Aristotle,

and had argued that reason and religion could be compatible.

However, the caliphates, anxious never to depart from the literal words of God,

made sure that Averroes's ideas would be banned

and his books burned.

Aquinas knew that the Muslim world's increasingly radical rejection of reason

was harming what had once been its thriving intellectual culture.

And it was overwhelmingly thanks to Aquinas's ideas

that Christianity did not suffer the same process of stultification.

Though Aquinas was a man of deep faith,

he provided a philosophical framework for open scientific inquiry.

He reminds us that knowledge can and should come from multiple sources,

from intuition but also from rationality,

from science but also from revelation,

from pagans but also from monks,

that sounds obvious, until we notice just how often

civilisation has been and is still being harmed by people's refusal

to take this brilliant idea on board.