Human judgment frequently operates at a subconscious level. Many of the judgments we make are not the result of conscious, deliberate thought. Nevertheless, it may be helpful to consider how human judgment works.
Human judgment is the application of a standard of judgment to an object of judgment. One example is the judgment of whether one is permitted to proceed through an intersection. Having already judged that there is an intersection ahead, and having judged that the intersection is controlled by a signal, one may make a judgment about whether the signal permits one to proceed through the intersection.
The government normally aims to make this an easy judgment. Traffic lights are supposed to be perspicuous. Thus, rules for interpreting traffic lights are simple and widely distributed. Additionally, the facts that are needed to be known in order to arrive at a correct judgment are also made plain.
In making the judgment about whether one is authorized to proceed through the intersection, one must interpret the traffic laws and one must interpret the light signal, and one must make a comparison. At a fundamental level, the traffic laws are typically written in a very easy to understand way, such that if the light is red, one is not authorized to proceed, and if the light is green, one is authorized to proceed.
For folks with good color vision, this makes it easy to figure out whether or not one is authorized to proceed. One interprets the color of the lights, one applies that to one's interpretation of the rules, and one concludes either that one is authorized or not. For folks with color blindness, this process may be a little more challenging, since they may need to use something else (such as the intensity or location of the light) to deduce the color of the light. Yet most people are still able to regularly come to a correct conclusion about whether they are authorized to proceed.
This is a relatively simple example. Human judgment can be a lot more complex in other cases. For example, judging whether or not Benedict XVI's latest "Apostolic Exhortation" is theologically correct may require one to make significantly more difficult judgments, both in terms of interpreting the standard (Scripture) as well as the object (the exhortation).
Thus, the thing by which we judge ("the standard") is Scripture. The thing being judged ("the object") is the teachings of the pope. In the process of judging the object by the standard, we must interpret both the object and the standard. Yet, we should not confuse the interpretation with either the object or the standard.
In other words, the true standard is the Scriptures, not our interpretation of them, just as the true object is the teaching of the popes, not our interpretation of them. We may err in our judgment due to an error either in understanding the standard or the object.
This may be easier to apply in the traffic light situation. While the red and green light situation may seem to present relatively clear rules, folks sometimes interpret the law in ways that they find convenient. Normally folks do not interpret the rules to make stopping for red optional, but perhaps they will interpret the rules to suggest that if the light is just turning red and they can make it through without inconveniencing anyone, this is ok.
Alternatively, sometimes people make mistakes about the object. For example, in a city where the lights are placed horizontally rather than vertically stacked, a colorblind person may erroneously think that the order of lights is left to right rather than right to left, and consequently may make an incorrect judgment.
Getting back to the example of judging papal teaching, both types of errors are possible. It is possible to misunderstand (for a variety of reasons) what the Scriptures say about a particular subject, and it is also possible to misunderstand what the pope is saying on a particular subject.
Advocates of Rome are fond of saying that appeals to Scripture are appeals to one's interpretation of Scripture. This comment confuses the issue of the standard and the application of the standard. Interpretations of Scripture (and of the object) are involved in applying the standard, but the standard is Scripture.
This is a significant distinction because the interpretations of the standard are able to be corrected by appeal to the standard. Thus, we can legitimately correct someone's misinterpretation of the traffic laws by appealing to what the traffic laws actually say. Likewise, we can legitimately correct someone's misinterpretation of Scripture by appealing to what the Scriptures actually say.
The same is true with respect to the object. We can point out that the light is actually green (not red), as people are wont to do at intersections by honking their horns at the stopped driver in front of them. Likewise, in theological discussions we can point out that our critic has attributed a position to us that is not our position. Thus, while his interpretation of the standard may be correct, his interpretation of the object is not correct.
Understanding human judgment, we can more easily answer the objections of Rome's adherents who attempt to persuade us to exercise human judgment in favor of them and/or their church, while complaining about our use of human judgment when it leads to conclusions that are contrary to their position or that of their church.