Image caption Our ancestors' views and social mores were very different

Everybody thinks they know what's right and wrong. But will things that seem moral today be deemed completely immoral later, asks David Edmonds.

"Women should leave reasoning to men. And they are not fit for serious employment."

Happily not sentiments one hears very often these days. But there was a time when such views were far more conventional. These are the opinions of the 18th Century Prussian, Immanuel Kant, one of the most influential philosophers in history.

So how should we think about Kant in the light of his judgements about women? Assessing attitudes and behaviour in the past presents us with a puzzle. What we might regard as offensive today - sexist, or racist, or homophobic for example - might have once been orthodoxy.

A moral relativist would say that our values today can't be compared with the values from another era. What was right for them was right for them. What is right for us is right for us.

Find out more The Philosopher's Arms was broadcast on BBC Radio 4 on Tuesdays at 15:30 BST Or catch up with iPlayer

The philosopher Miranda Fricker is not a moral relativist, but she thinks the test for blameworthiness is whether the person could have known any different. "The proper standards by which to judge people are the best standards that were available to them at the time".

It's unfair to blame people for failing to be moral pioneers, she says. "The attitude of blame presupposes that the person was in a position to have done better."

But if we can't blame people for abhorrent views, does that also mean we can't hold them responsible for these views?

Influenced by ancient philosophy, the 20th Century British philosopher, Bernard Williams, tried to tease apart a distinction between blame and responsibility. He did so by writing about what he called "moral luck".

Another kind of bad moral luck is being born at a time when you'd need to be a moral genius to see that a certain view or practice is wrong, because all around you are people who accept that the practice is alright Miranda Fricker

Take the following example. Imagine that while a lorry driver is on the road a child suddenly runs out in front of him. Through tragic bad luck the child is hit by the vehicle and dies.

The man is blameless, for the accident has happened through no fault of his. In this sense he has nothing to reproach himself for, and has done nothing wrong. And yet, writes Williams, surely this man is now enmeshed in a set of moral responsibilities that, for example, a bystander, who is equally blameless, is not.

It makes a moral difference that it was him at the wheel. As the driver, he might have an obligation to meet the parents or attend the funeral - obligations not incurred by a bystander.

This is one kind of moral luck, or moral unluck. "Another kind of bad moral luck is being born at a time when you'd need to be a moral genius to see that a certain view or practice is wrong, because all around you are people who accept that the practice is alright," says Fricker.

These issues of blame and responsibility are relevant for reflecting on how we make amends for historic moral mistakes. For years the Australian government refused an apology to its indigenous peoples - in particular for the practice of forcibly removing children from their families.

It seems utterly shocking now, but it involved thousands of children and continued for decades. It was the current Prime Minister, Kevin Rudd, who finally made the formal apology on behalf of the state in 2008, against the wishes of a significant minority of the Australian people. Here is an example where, arguably, the current state might be blameless, yet somehow responsible

Image caption Should the UK apologise for slavery or celebrate its role in abolition?

Similar controversies arise over whether the UK should apologise for its role in slavery, and whether people like Alan Turing should be posthumously pardoned.

Turing, the brilliant mathematician who among other things helped crack the Enigma Code in World War II, was one of many people charged with gross indecency in 1952, under laws criminalising homosexuality.

He killed himself two years later. "It seems to me to be a measure of civilisation that our institutions have full accountability, in much the way that individuals do," says Fricker. "An apology is an incredibly important act that our institutions should increasingly become capable of - people who have been wronged by the state are owed an apology by the state, even if the individuals in government are different from those at the time."

Image caption Kant might think differently if he were alive today

Immanuel Kant, of course, was writing in the 18th Century. But the way attitudes to homosexuality have so rapidly evolved in the UK and in some other countries, shows how morality can undergo a revolution within a generation.

It may well be that the young or middle aged people of today will, in future decades, look back at views they once held and feel horrified and ashamed. And just as we judge Kant's century, and identify its moral defects, so it is inevitable that the people of the 23rd Century will detect flaws in ours, the 21st.

What might these flaws be? Our treatment of the environment? Our tolerance of poverty?

Fricker thinks that in the not-too-distant future we'll be shocked by the way that we, in the early part of the 21st Century, still treat animals. "I hope that some of the ways we currently still treat animals, the way that we factory-farm them, for instance, will seem completely unbelievable and unacceptable."

What else might our descendants condemn us for? If enough of us know the answer to that today, we really have no excuse but to act on it today.

The Philosopher's Arms was broadcast on BBC Radio 4 on Tuesdays at 15:30 BST or catch up with iPlayer

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