Another core idea in Logic-- in general, as well as in logic for theological discussion-- is Consistency.
The fundamental definition of consistency is this: two or more ideas may be true at the same time, in the same context. If two statements can both be said to be true at the same time and in the same context, they are said to be consistent.
All of us are inconsistent. One of my philosophy professors pointed this out in a profound-- and humorous-- manner: “everyone is inconsistent; even a determinist will ask you to pass the salt!”
But our inconsistency matters the most when we attempt discourse and discussion-- particularly when there is disagreement involved. This is because our inconsistencies undermine our more salient points by causing others to question, second-guess, or even outright doubt all of our points.
A couple of recent political events demonstrate inconsistency well. For one, John McCain stood up on Monday, September 15, and declared that our economic system is “fundamentally sound” while addressing the concerns about the Lehman and AIG failures. (He has since backpedaled on that statement, which further underscores the inconsistency.) Meanwhile, Senator Obama (and the rest of the Democrats in congress) have strongly supported a bailout plan approaching $700 billion-- money which will effectively buy off the financial problems of the wealthiest of Americans-- while simultaneously demanding an increase in taxes for the wealthiest Americans. (I guess that is their plan to pay for the bailout.)
Similarly, the entire financial crisis is being blamed largely on the economic policies of President Bush, while President Clinton’s presidency and economic accomplishments have been lauded and praised. But the crisis we are facing now is the fallout of poor policies of a decade ago, just as a significant amount of the economic prosperity of the Clinton presidency was the fruit of the presidencies that preceded him. It turns out that what we do today actually has impact on tomorrow-- go figure.
A good example from the theological discussion world covers the debates of the past decade or so in the PCA. Back in 2002, the debate du jour was over “good-faith subscription” vs. “strict subscription.” A number of guys opposed the idea of good-faith subscription because, some of them said, it would open the door for too many differing positions on various theological issues. Fast-forward to 2006, and the new debate has turned to a theological view called the “Federal Vision” position-- which was, and is, a variation on the historic position on the prominence of individual salvation. Ironically, many of those who came under fire during the Federal Vision debates, and who took cover under the “good-faith subscription” blanket, were some of the same guys who opposed the passage of the good-faith subscription amendment. In short, many of the same men who would end up benefiting the most from the good-faith subscription vote were those who spoke most vehemently against it.
The difficulty about consistency is that it can’t easily be corrected or improved. Unlike bad argument styles, for example, you cannot simply evaluate arguments by asking a set of questions that will reveal the problems of consistency. To recognize inconsistency in your own arguments, you must begin to learn how to see how ideas connect. You must also develop a memory of what you have said and done, and recognize how those things affect the next thing.
Unlike fallacies, however, defeating inconsistencies doesn’t really require strategies or counter-examples. It simply needs to be pointed out. Once you’ve shown someone to be inconsistent, they will often make things worse by disclaiming, excusing, or digging deeper.