There's been a fair bit of fury on social media in recent days about original sin. Not something I would necessarily have predicted in the window between the budget and COP26!

Original sin is an essential piece of Christian doctrine. If you are a Christian, you should not be squeamish about it, and if you are not a Christian then I suggest that you should be a lot more open to the notion than you probably are.

Original sin comes from the Genesis account of the 'fall' of humankind. This was the choice made by human beings to tell God that they wanted all the good things that He had made, but that they didn't want Him. It was the choice humans made to turn their back on the perfect God who made them and loved them, and to set themselves up as their own gods.

The doctrine says that from that moment on, all human beings became flawed; not just limited but flawed. Capable of good, of course, but with a default towards selfishness and towards wanting God not to be God, not to exist and not to have any claims on them.

Centuries upon centuries of experience tell us that human beings are pretty flawed and capable of being both good and bad, and that human-inspired tragedy, want, heartbreak and abuse affects every generation and every family. If your objection to the notion of original sin is that you think humanity is basically good, then I admire your optimism but doubt that you've ever been outside your front door.

The fact is that original sin tells us something important when it comes to justice. It tells us that human beings are responsible for the wrong that they do.

If the materialists are right and if you do something awful, then logically it's not really your fault is it? You are just the product of bad genes or an unfortunate environment imposed on you by those around you.

But can we really blame 'bad' genes or environment? A godless conception of good or evil is intellectually riddled with holes, because without a god and a natural law then there can be no good and no evil. Everything is neutral. When a comet ploughs into a planet, it's not being evil: it's just blindly doing its thing. Without a concept of sin and the doctrine of original sin, good and evil must simply be arbitrary and temporary constructs. They may serve some biological evolutionary purpose for now, but they have no moral underpinning in this accidental universe in which we accidentally exist.

Original sin tells us that you can't get away with the luxury of that belief; that you are indeed responsible for your actions.

Those who would call themselves liberals ought to be especially careful in dismissing original sin because it is one of two Christian doctrines - along with the doctrine of humans having been created in the image of God - that underpin our Western liberal values.

One of these doctrines is positive: all people are equal in value. But more than that, each individual has an impossibly huge value, bearing the dignity of being at the apex of God's creation.

The other doctrine – original sin – is negative, but just as important because it tells us that we are responsible for the wrong that we do and that we should be held to account.

These two Christian doctrines are the foundation of liberal democracy: equality and justice. The values of our society would never have developed without them. So we should be very careful about sneering at either of them.

In the end though, the objections to the notion of 'original sin' are – ironically – based on the reality of original sin, i.e. that we don't want God to be God. We don't want sins to exist, or at least if there are such things as sins, we want to decide what they are. Which is, once again, human beings rejecting God and putting themselves in His place.

Finally, this whole thing blew up because Katharine Birbalsingh used the term 'original sin' to make the point that children should be taught that we are all flawed and need to learn right from wrong.

Well, shouldn't children be introduced to a range of world views, not just the ones we find comfortable and easy? Indeed maybe the reason we find original sin uncomfortable and difficult is because it hits a raw nerve. 'Sin' is an inflammatory word in our society.

The common – and utterly wrong – view of original sin is that it means children are born evil and have to spend their whole lives trying to atone for this. It is seen as a medieval attempt to keep people in guilt and obedient to church authority, which has no place in the 21st century. This misses the whole point that God loves us despite our flaws and failings. He is not waiting for us to get our lives in order before He will notice us. Instead He gets alongside us just as we are.

But more than that it is controversial because what it does say is that, actually, we cannot save ourselves. This is both liberating and humbling. Liberating because it means I don't have to spend my life weighed down with guilt, trying to become perfect to be accepted. Humbling because it reminds me that I should not judge others for their flaws when I have plenty of my own. And because it shows me that I cannot be god – I simply do not have it in me to become my own saviour.

This kicks against everything our society tells us, but there is immense richness to be found in stepping back to consider a world view that has empirically been shown to hold water throughout the last two millennia.

Tim Farron has been the Member of Parliament for Westmorland and Lonsdale since 2005, and served as the Leader of the Liberal Democrat Party from 2015 to 2017. Tim is also the host of Premier's 'A Mucky Business' podcast, which unpacks the murky world of politics and encourages believers around the UK to engage prayerfully. You can find it on your chosen podcast provider.