The Tea Party is not crazy nor are those who oppose them (let’s call them “the establishment”) unprincipled “collaborators” with Democrats. But that’s how each side views the other. And the reason for that lies at the heart of the most consequential political struggle in more than a generation — a civil war in the Republican Party that threatens its very existence.

Why should this be so? An objective look at the positions both sides take on the issues would reveal very little difference between them. This is especially true when looking at the broad sweep of policy on taxes, regulations, individual liberty, and the size of government. On individual issues like immigration reform or foreign-policy matters, the differences are vast but not unbridgeable — at least not as vast as the difference between Republicans and Democrats. Both sides also share broadly similar values, religious beliefs, and a common way of viewing our history and culture.

The impetus that is driving this war that becomes more bitter and personal almost every day is to be found in the way each side views and interprets reality. Not the kind of substantive physical reality in which we all exist, where two people standing side by side look out a window and both agree they see a tree. Both agree the tree has green leaves shaped like a maple leaf. Both agree the sky is blue. There is no disputing substantive reality (although the intensity of the colors green and blue might be interpreted differently by our observers).

Rather, what divides the Tea Party and the establishment is what’s sometimes called Weltanschauung, or worldview. This is reality as it is interpreted communally when facts, ideas, people, and events are filtered through an ideological or philosophical prism. Epistemological questions about “what is true and what is false” can be answered differently depending on how one’s worldview has been shaped by experience and knowledge. In this sense, while there may be an objective “right or wrong” there may not be an agreed upon “true or false.” It is the metaphysically subjective interpretation of the objective reality of ideas and events that divides the Republican Party and threatens to blow it apart at the seams.

Both the Tea Party and the establishment believe Obamacare to be bad: coercive, ruinous to the economy, injurious to personal liberty, and inimical to our founding principles. No Republican voted for it. But in compromising to re-open the government and raise the debt ceiling, the establishment is viewed by the Tea Party as having betrayed “principle.”

Why? Erick Erickson explains:

Men like Mitch McConnell, John Cornyn, Eric Cantor, Kevin McCarthy, and others have preached a great sermon against Obamacare, but now conservatives who supported them see that these men have refused to actually practice what they’ve been preaching. They’ve refused to stand and fight with the rest of us.

The fight was always about Obamacare. Today we know we must keep fighting and fight harder against even our own supposed side. But we always knew the fight would force the charlatans of the GOP out of the shadows into disinfecting sunlight. It has happened as I wrote it would almost a month ago.

In the Tea Party’s reality, Obamacare is so bad as to be catastrophic; indeed, a default might be preferable to the implementation of the ACA. And to “stand and fight” — even though there was no chance of success — was worth whatever cost to the party politically, or the cost to the economy in keeping the government shuttered. Anyone opposing this position is a “charlatan” — despite the fact that the charlatans all voted against Obamacare and would defund it in a second if it were at all possible. (Note: It’s nonsense to think that Erickson and the Tea Party didn’t know who every single one of the “charlatans” are. That kind of hyperbole is not meant to inform, but to rabble-rouse.)

The reality inhabited by establishment Republicans is decidedly different. What the Tea Party sees as naked betrayal, the establishment sees as responsible governance. The irony is that the Tea Party will counter that trying to defund Obamacare is real responsible governance. Two worldviews, two notions of what constitutes “responsible” governing — and no way to bridge the divide between them.

To someone not imbued with the ideological fervor of Tea Party Republicans, or existing in their reality, it seems delusional to believe some of what they believe. Erickson again:

The establishment has given conservatives a brilliant opportunity to advance against them and then against the Democrats. As Obamacare now goes into full swing, conservatives can show that they tried to stop it while Mitch McConnell and so many others sat and watched from a cozy booth the Capitol Hill Club leaving the fighting to others while they did everything possible to undermine the fight.

As more Americans watch Obamacare fail them through the Republican primary season, conservatives will be able to put the focus on Republicans who funded Obamacare instead of fighting it. Whether they like it or not, Republicans in Congress will find their names on ballots in 2014. They cannot hide or escape fate.

At some point, there has to be an appeal to an objective reality in which most agree what is real and what is not. (It doesn’t necessarily mean that what most agree is real is actually “true,” but for political purposes where perception counts for so much, objective reality serves a purpose.) Most Republicans, Democrats, and independents opposed defunding Obamacare. There was no “fight” to defund Obamacare because, technically, legislatively, and practically speaking, there was no chance of that happening. Whom or what was Cruz et al. fighting? In order to fight, you’ve got to have two sides engaged in combat. Cruz shadow boxed an idea — the legislation known as Obamacare — for 21 hours and may have cheered the Tea Party but he accomplished nothing. The same would have held true if every other Republican senator — including the charlatans — had spoken against Obamacare for 21 hours each.

But the sincere and real feelings of betrayal felt by Tea Party Republicans can’t be dismissed by the establishment if the rift is going to be healed. Of course, if Erickson and the Tea Party follow through on their threats to primary establishment Republicans who didn’t display the proper amount of ideological purity in the futile effort to defund Obamacare, the level of frustration on both sides will rise to dangerous levels. When most Tea Party primary candidates are ultimately defeated (the power of incumbency is considerable) and most establishment candidates who were primaried end up spending a small fortune just to remain on the ballot, the possibility of a serious and permanent breach might be the outcome.

Two worldviews defining reality differently have brought the GOP to the brink of fissure. What one side sees as true, the other sees as false. What one side sees as reasonable, the other sees as delusional. At this point, they are as ships passing in the night with little hope of healing the breach before the 2014 midterms.