"Ignorance is not merely the lack of knowledge, but self-destructive turning away from truth in all areas of life. Persons develop a taste for ignorance, the predisposition to embrace erroneous beliefs based on presumption or mere authority. The ignorant person believes he knows what he actually doesn't know. He becomes delusional. He is deranged." So declared Plato, unwittingly describing the face of 21st-century American conservatism in the age of Obama. Today, facts and fiction appear more interchangeable than ever before in America's public discourse.

In the most recent example: Republican congressman Joe Wilson, after being officially censured for interrupting and yelling "You lie!" at Obama during last week's healthcare address to Congress, took it as badge of honour. He pledged on his Twitter feed on Tuesday that "Despite Congress' actions today, I will not back down from speaking the truth. Please stand with me," before asking people to donate to his 2010 campaign.

Apparently it doesn't matter to Wilson that his heckling of the president, disgraceful as it was in its decorum, was based on pure fiction. Obama has never advocated insuring illegal immigrants. In fact, his bill explicitly bans it. Regardless, Wilson continues to flaunt his assertion unapologetically – and it has made him a hero among the radical right.

That's what's most disturbing about this ordeal: It shows that Americans can no longer agree on basic realities. Certainly everyone's entitled to their own opinion, but not everyone's entitled to their own facts. We can't have a serious debate about policy in this country when one group keeps inventing its own version of the truth.

It doesn't matter to Sarah Palin that her claim about healthcare "death panels" was a flat-out lie. She continues to tout it after being repeatedly taken to task – including by the Associated Press and the very fair FactCheck.org. With no admission of her falsehood, millions of people still believe it, and the national dialogue remains tainted.

It doesn't matter to Michael Steele, the chairman of the Republican party, and his cohorts that healthcare reform will only create more choice and competition in the form of a public insurance option. They continue to claim it'll lead to a "government takeover" of the system and more "rationing" of care. Their insistence on these erroneous claims fuelled the teabagging and town hall madness this summer.

It doesn't matter to the birthers that Obama's official birth certificate from Honolulu, Hawaii has been thoroughly examined and verified. Their virulent anger toward this alleged Muslim socialist from Kenya remains immutable. Even more stunning is that nearly two in three mainstream Republicans harbour doubts as to whether he's a natural-born US citizen. There couldn't be a clearer sign that some people simply refuse to accept reality.

It's one thing to cynically lie for political purposes and later take the punch if you get caught – another to cling to the lie after it has been exposed. This is a major abdication of responsibility for public figures, and it serves only to feed the paranoia of a generation of troubled souls unable to come to grips with a country changing before their eyes – demographically and ideologically. While previously the exception, this is quickly becoming the norm in today's Republican party.

Thus we live in an era where, in the depths of ignorance, facts are no longer treated as facts. Outlandish notions are portrayed in the media as legitimate points of view. Debates over credible but differing opinions are being replaced by shouting matches over easily verifiable facts. The truth can so easily be parsed or even snubbed for political gain, and far from facing repercussions, the perpetrators are often rewarded with widespread press coverage and devoted followings.

It's true that this mentality predates Obama. The usual suspects have snubbed science for decades – evolution is merely a theory, and global warming is a leftwing conspiracy. There's a reason scientists and intellectuals, in their affinity for truth, are rapidly deserting today's Republican party and conservative movement. But, the sheer volume and depth of the craziness appears to have escalated to unprecedented levels.

Thomas Jefferson famously said: "If a nation expects to be ignorant and free, in a state of civilisation, it expects what never was and never will be." The fabric of American civilisation now faces one of its its toughest tests to date. Only time will tell whether it can it re-emerge from the darkness of ignorance.