One of the most frustrating aspects of my work as an apologist is when I am asked to provide an inquirer with a resource on a particular subject that is "one hundred percent faithful to the magisterium of the Catholic Church" and by someone who is "absolutely orthodox." Oftentimes, I may know of a particular resource that would be helpful, but am reluctant to recommend it because it is not "pure" from an orthodox perspective or by someone who can be considered totally orthodox.
Take, for example, John Allen, who is a Vatican correspondent for the National Catholic Reporter. He is a very good resource for reasonably fair information on current Vatican affairs. As far as I am concerned, his book All the Pope’s Men should be on the required reading list of all aspiring apologists, particularly those seeking to explain why the Vatican takes certain actions that do not seem logical to the ordinary American Catholic. But, because of his credentials and his somewhat center-left approach to Catholicism, I either cannot recommend him much of the time or must load any such recommendation full of caveats. This is not because of a particular flaw in Allen or his work, but to explain to an inquirer exactly what can and cannot be recommended about Allen and his work.
What I have found is that many of the orthodox Catholic inquirers I deal with are very cautious about whom they will listen to or read. A particular author or speaker must offer a book or tape that is either one-hundred-percent orthodox — according, mind you, to this particular person’s perception of orthodoxy — or the resource is anathema. This is an understandable and even noble impulse because the Catholic in question is doing his best to avoid falling into error about the faith. Nevertheless, it is misguided. Let me explain why:
If one limits his exposure to the faith only to those individuals who one is certain largely conform to one’s own understanding of the faith, it is unlikely that such a person will ever grow beyond his own understanding of the faith. Applying "purity tests" to any and all resources that one will consider and automatically rejecting any that fail the exam means that one cannot benefit from the legitimate insights others may offer.
Rather than "purity tests," what orthodox Catholics should consider developing are "purity filters." Learn the faith well enough from orthodox sources to filter out the impurities while still accepting and benefiting from the good stuff an otherwise problematic resource can offer. If there is a question about whether a particular idea or claim is valid or should be trapped by the filter, then call on orthodox resources — such as Catholic Answers — to help figure out what the Church teaches or requires on the subject. A particular resource may end up entirely worthless and be thrown out. Some stuff, though, may be problematic but still useful.
For example, as a Catholic woman who hopes one day to marry and raise a family, I do a lot of personal reading on marriage and parenting. Believe it or not, one of my favorite parenting books is Becoming A Jewish Parent by Daniel Gordis, a Conservative Jewish rabbi. There is, naturally, some information that is either not helpful to me as a potential Catholic parent or follows a more liberal religious approach with which I do not agree. But, as one example of something helpful to Catholic parents in the book, Rabbi Gordis’s approach for teaching parents how to raise their children to marry Jews and raise Jewish families could very easily be adapted by Catholics seeking to raise children who will marry other Catholics and raise Catholic families. A Catholic using a "purity filter" can sort out what is unnecessary for Catholic parenting and take away Rabbi Gordis’s insights that are helpful to any religiously-committed parent.
“Do not quench the Spirit, do not despise prophesying, but test everything; hold fast what is good, abstain from every form of evil. May the God of peace himself sanctify you wholly; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ” (1 Thess. 5:19-23).



