D. Q. McInerny’s Being Logical: A Guide to Good Thinking answers a long-standing need for a concise book on this fundamental topic. It also helps that the author is a conservative. Having said that, however, philosophical affiliations are no guarantee of sound reasoning.
First, we should never become so impatient that we rely on enthusiasm to win an argument. Says McInerny: “What should move people in a sound argument is its intellectual substance… not whatever emotional overtones the argument may carry with it.” Many people, including conservatives, make up for poor rhetoric by padding their chatter with emotive outbursts.
Second, we are frequently snagged by the confusion between the truth of an argument and its validity. The latter refers to the structural integrity, or the coherence, of the argument, not its content. Hence any false premise (within a valid logical statement) will yield a false conclusion. For example
The ruling class is oppressive.
Heterosexual males are members of the ruling class.
Therefore, all heterosexual males are oppressive.
That is the dilemma of logic subordinated to ideology. Yet how many political or theological traditionalists are hampered by ideological baggage as well? In political discussion, some terms like justice or equality admit of potential ambiguity, notes McInerny, “not because they have no meaning but because they are especially rich in meaning.” The temptation is to use labels in place of cogent definitions, to beg the question with unsubstantiated assertions or to engage in special pleading. One would need to verify a broad statement like “The Church condemns capitalism.” This claim could have a basis in fact—few people enter a debate telling outright lies—but are the premises sufficient to uphold the assertion?
There are also dangers in arguing from authority or expertise. “The views of a world-famous musician on subjects such as the economy or global warming,” warns McInerny, “carry no special weight if the only authority behind them is the musician’s musical accomplishments.” Along those lines, in an economic debate it is not enough to assert that “So-and-so was an orthodox Christian, he opposed the free market system, therefore we should do the same.” A case of unverified testimony (rather than facts) is of no more value than Dr. X’s endorsement of a leading toothpaste.