Not so long ago it was common at a dinner party with family and friends to find ourselves drawn into discussion and debate over the political and moral topics of the day. There was usually a lot of strong feeling, praise for good arguments, some good-natured ridicule for bad ones and, of course, heated support of one's own ideas. But I cannot remember any violent personal attacks, tears or outrage over someone else's point of view, however wacky it may have seemed, and that was because no one interpreted disagreement as offensive. Most striking of all, most people then were unafraid to state their own views, even happy to volunteer them. There wasn't the slightest hint of worldview "political correctness" in the air. We assumed that was a moral disease of the Red Chinese, a million of whom I can remember seeing displayed on a centrefold of Life magazine in Tiananmen Square, all in black Communist uniforms, all waving Chairman Mao's Little Red Book fanatically in the air. The mere notion of human-rights tribunals such as we have now in most Western nations, set up by governments to "re-educate" and to control or punish thought and speech in a free country, was simply unthinkable. We were quite aware that many post-war immigrants fled from the disease of totalitarianism to the "free" world to escape that very thing. But the disease followed them.

A similar dinner party today is a very different story, almost certain to illustrate the Great Divide that is the topic of this book. The elephant in the room, as the saying goes, will almost certainly be an unspoken awareness that there are a lot of political, social and moral issues that most are afraid to mention. The silence — who has not felt it? — tells everyone to keep their true thoughts to themselves. Share only unimportant, or even insincere, thoughts. This may be typical in the company of complete strangers, about whom we may care nothing. But to find it true among family, friends and in our own close communities is very new and very sad, for it tells us that civil society, if not quite at an end, is comatose, that we are becoming strangers to each other. This book is one man's effort to change this situation, to help people become unafraid once again.

I hasten to add that it is not a book about politics or political parties — fickle things at the best of times. For I believe that the political history of the West (which we assume is being decided by all the party, policy and election language with which we get bombarded) is in fact an outcome of a much deeper and less obvious ideological warfare. Volcanoes and earthquakes are a surface sign of invisible geological forces, just as shifts in the political, social and moral worlds are surface signs of invisible ideological forces.

In his best-selling book The Clash of Civilizations, Samuel Huntington warned us about the clashes to come between the West and other, incompatible civilizations. The attacks by puritanical Islamists on our deeply secularized, overly sexualized, highly materialistic culture on 9/11 and since have borne out his predictions.

This book is more concerned about a much less obvious but more pervasive war of moral and political ideals within Western civilization itself, because from Pittsburgh to Paris, Buenos Aires to Buffalo, Vancouver to Venice, we have been engaged in a civil war of values and principles for a very long time. At bottom it is a war between two incompatible political cultures, or enemy ideologies, concerning the best way to live; and I suspect that with a little effort this conflict may be found simmering beneath the surface of all civilizations, waxing or waning as historical circumstances allow.

For reasons professional historians are better equipped to explain than I, however, these two visions — today they are called liberalism and conservatism — emerged with extreme revolutionary violence in 18th century Europe and have been either simmering in peacetime or boiling over in various wars and revolutions ever since. During the 1960s, due to a growing post-war loss of confidence in the once unifying bonds of Western civilization, the tension between these warring ideologies surfaced again as a moral, political and theological divide that has continued to separate us from each other over what used to be our dearest shared conceptions of truth. This divide is now everywhere felt (the fear on both sides, to speak honestly, is a sure sign of it), if not everywhere clearly understood; and it has more to do with disagreement about means than ends.

The main hope of this book is that by bringing the underlying differences lurking in the silence of the Great Divide to the surface, readers will be more prepared to engage over the real differences in their philosophies of life, rather than choosing to go silent and then slipping back into the divide. Surely it is better to hear two people debating and exploring the deeper differences in their conceptions of democracy, say, or of human nature or the role of the family in society, and how and why these necessarily give rise to a different politics, than to watch them working up personal attacks on each other or angrily shutting down the entire discussion. A rather curious fact is that both sides of the Great Divide seem often to have the same ends in mind, but argue frustratingly over very different notions of the best means. It is as if they are using different languages to explain something important to them both. Here are just a couple of examples.

Modern liberals and conservatives both agree that children need moral influence. But they cannot agree on whether it is better that the main influences be parents, family and religion (the conservative view) or the secular state and its schools, agencies, counsellors and sex-ed programs (the liberal view). On this question, I once heard a serious liberal politician argue with passion that the children of the nation do not belong to their parents or families; they belong to the nation, they are a resource, just like our oil or coal. Hillary Clinton mouthed this same sentiment when she said, "There's no such thing as other people's children." For many liberals (so this line of thinking goes), it is the state and its professional educators and psychologists (as "change agents") who ought to lead the way in child and social development, and not parents, who are amateurs and should be licensed before being allowed to reproduce. There has been a long and continuing struggle in the West between such opposing assumptions.

Or again, both sides will agree we all want less crime. But because modern liberals and conservatives have irreconcilable conceptions of human nature (as we shall see), the liberal will advocate spending more money to fix up bad public housing, while the conservative will say this is to miss the point: the real cause of crime is not the house, it's the home. It is the badly weakened moral fabric of the community and of the people living in the house that make it not a good home. Between the standard liberal and conservative conceptions of those two words — house and home — lies a yawning divide.

Many such underlying liberal/conservative disparities and divisions will be examined as I attempt to show that no matter what surface arguments someone defends, we can usually tease out their underlying philosophy of life and show how it always obliges the taking of specific moral and political positions at the surface to prevent the underlying belief system from crumbling. Most defenders of their own arguments sense this threat intuitively, signalled by some thought such as "What did I just say? My whole case is going to collapse!"

In the example given, the liberal who insists on more public funding to repair public housing is forced by his own logic to adopt this "solution" because a commitment has already been made to the belief that, as all human beings are fundamentally good and equal by nature, whatever is wrong or bad in individuals or their communities must have an external cause. So it follows, as the night the day, that he will be obliged to call for better laws and more government funding (external cures for what are perceived as externally caused problems). These means-ends differences do not come about just because there is a shift in perspective, or for any other lightweight reason. They have a deep ideological root that is worming away beneath surface perceptions. Nothing "shifts" without underlying reasons.