They arrived at an inconvenient time, I was hiding in a room in my mind.

Just before Christmas I started writing about arguments and promised to write more about the mistakes we can make we can make in our search for the truth. Today I wanted to write about the dangers of received wisdom.

Most prejudice begins life as received wisdom; messages that we have received growing up from parents and peers along with all sort of perfectly useful information. If you grow up aware that you should never to journey into The Old Tooth & Claw Pub on a full moon, you’re probably better off than if you had to find out by yourself. And if your parents told you to never play cards with a Frenchman, you may well tell your own children to never play cards with a Frenchman. You never played cards with a Frenchman, and as a result, you were never cheated at cards - at least not by a Frenchman.

When we consider our own history and the history of prejudice, we like to concentrate on those occasions where prejudice has lead to full blown atrocity, and in particular, we like to concentrate on the genuine sadists of those stories. The slave-masters or concentration camp guards who performed acts of violence and brutality which you and I feel pretty sure we could not have brought ourselves to do. Because we are nice people. We are intelligent people.

We don’t like to think about the nice, intelligent people who nevertheless did participate in these atrocities, as well as the ongoing inequality and oppression that provided a sociological springboard for them. This is not to take the responsibility of their actions on our shoulders. However, we do need to acknowledge our own fallibility.

The great sin of those who remain prejudiced is a failure to challenge received wisdom.

Just how great this sin is depends on context. If you were an ordinary working person living in eighteenth century rural Britain and you’d never seen a black person, but you’d heard tell of godless savages, cannibalism and witchcraft in Darkest Africa, you really wouldn’t have a lot of reason to think very hard about the ethical questions surrounding colonisation and slavery. You’d also have very little power to change things if you did.

It is however quite difficult for us to imagine a person coming into contact with slaves and failing to see their own reflection in one another's eyes. But some people – many people – choose not to question their thinking in the face of massive evidence which suggests it may be in error. This not because they are malicious, unintelligent or mad, but because they have an awful lot to lose; sometimes materially or politically, but more often it is purely psychological. The fear of the prejudiced can probably be summarised in three trains of subconscious thought;

1. (a) I am better than this person. The possibility that this person is equal to me represents the possibility that I am not as good as I hope I am.

1. (b) This person is completely different from me. The possibility that this person is not so different from me represents possibilities about myself which I do not wish to entertain.

2. This person is my enemy. The possibility that this person could be my friend represents the possibility that bad luck or poor decisions have lead to the misfortune or dissatisfaction in my life.

It is easy to see how 1(a) operates in sexism and class prejudice. The idea that you may have lead a privileged life and that others who have less are just as bright, capable and virtuous as you are is a pretty scary one. 1(b) is perhaps at the heart of both disablism and homophobia – although homophobia cannot exist in the absence of sexism; all these things are interrelated.

I would however suggest that 2 is the most powerful and dangerous, the one that fuels the fire of racism. Racism has manifest itself in extreme violence and cruelty on a much larger scale and on a far more regular basis than any other prejudice.

We all have misfortune in life, whether through our own mistakes, the mistakes of others or sheer bad luck. However, it is much easier to understand and cope with our own hardship if we have some focus for our distress, anger and frustration. And if this focus is a person, much better a caricature of an entire group, well then, that’s just super.

And it doesn’t take that much misfortune. Can’t get a job? Johnny Foreigner took it. Strapped for cash? Johnny Foreigner is costing you a wedge in tax. Anxious about crime? Johnny Foreigner is a law unto himself. Any fear or failure you experience in life can probably be traced back to Johnny Foreigner if you have the imagination. And we do.

We do. None of us are immune to this way of thinking. Sly Civilian has covered a number of instances where anti-racists and feminists have accused their opponents of being mentally ill. In other words

1. (b) This person is completely different from me. The possibility that this person is not so different from me represents possibilities about myself which I do not wish to entertain.

Which is deeply insulting to people with mental ill health, as well as an incredibly lazy way to view people who hold prejudice. If we simply dismiss their view, we will change nothing and are likely to become complacent of our own arguments.

The good news is that by acknowledging that the error is a logical one, we acknowledge that we can change our own thinking and the thinking of others in our pursuit of the truth.