In the September 2002 edition of the Journal of the Evangelical Theological Society, Scot McKnight’s article, "From Wheaton to Rome: Why Evangelicals Become Roman Catholic," offered good insight regarding the phenomenon of Protestants converting to Catholicism. The list included: (1) a desire for certainty, (2) a desire for history, (3) a desire for unity, and (4) a desire for authority.
Anthony then goes on to discuss each of these four desires. It should be pointed out that Scot's list leaves out the most important desire, the one that trumps all the others: the desire for truth. By this omission Scot implies that Protestants who become Catholic are doing so not primarily because of their desire for truth, and thus not because in their search for truth they believe they have found the true Church Christ founded, and in it the true doctrine of Christ handed down from the Apostles. In this respect Scot's deconstruction of Protestants who become Catholic implicitly treats them as persons who love something else more than truth, and are willing to sacrifice truth to attain it. That would not be a charitable assumption. In fact, it would be a subtle ad hominem, impugning the character of all those Protestants who become Catholic, and thus discrediting their decision to seek full communion with the Catholic Church.
In Scot's article we see that when converts to Catholicism talk about being motivated by a desire for the truth, he construes that as a desire for certainty. It is as though, for him, they aren't sacrificing truth for certainty; what they really want is certainty. But truth and certainty are not the same. Certainty is a subjective phenomenon, and many people who are certain about a position later come to discover that they were wrong about that position. Many Muslims and Mormons, for example, are certain that they are right. But presumably Scot would agree that Muslims and Mormons are in error in many important respects. Hence, since truth and certainty are not the same thing, it follows that the desire for certainty is not the same as the desire for truth. Therefore, Scot has indeed excluded "desire for truth" from his list.
Some forms of postmodernism construe the desire for truth as a desire for certainty, as though truth reduces to certainty, or is something entirely beyond our grasp as humans, and hence entirely beyond our capacity to desire or attain. Given that Protestants who become Catholic describe their journey as motivated by a desire for truth, an attempt to deconstruct their conversions as driven fundamentally by a desire for certainty, not for truth, deconstructs itself by revealing the influence of that postmodern philosophy.