When in debates, especially concerning theology, there is a tendency for each side to accuse the other of trying to switch topics. In a field as wide as theology, where different people have a wide number of interconnected beliefs which all build on and contribute to each other, having a discussion veer off course is to be expected. We should default to being gracious and not assuming malevolent intent, but not everyone does.
When one side accuses the other of intentionally using this strategy to ignore evidence, it may or may not be the case and it may or may not be intentional. One very quick way to figure out if it is intentional and deliberate is to refocus the conversation. If the individual refuses to refocus, then it is good indication that the matter is difficult for them to handle. They may be using obfuscation to avoid answering questions.
A good example of this would be when individuals try to debate about 1 Kings 22, a passage in which God uses deception to kill King Ahab. Someone trying to obfuscate will try to override the text by saying “God doesn’t lie” and may even point to verses that suggest as much. But the problem is that this does not clarify or explain the events in 1 Kings 22. Instead, the argument is “ignore the events in 1 Kings 22 because it contradicts what I believe from elsewhere.” That is obfuscation. Even if God never ever used deception, the events of 1 Kings 22 still need to be explained. On top of that, now the individual needs to explain it in a way in which God does not use deception. It complicates the text!
To deal with obfuscation, the best debate strategy is to continually refocus the individual to the text until it becomes readily apparent that they are avoiding it (note: this debate strategy will not win you any friends). If their obfuscation complicates the text, just tell them for the sake of the discussion that you will assume they are correct about their other beliefs. This doesn’t allow them to obfuscate and returns them to the original text, now having to deal with the text in the context of their belief (the original thing they wanted to avoid!).
But in some cases, accusations of “switching topics” are levied against people who are using other texts to clarify or illustrate points. Using other texts to clarify or illustrate points is perfectly valid, and would be no different than using hypotheticals to illustrate points. In a sense, using Biblical examples is better than hypotheticals because opponents feel much worse trying to dismiss the point. Hypotheticals should not be dismissed but regularly are. Biblical illustrations (in place of hypotheticals) make the debate strategy of dismissing evidence much harder.
Illustrations clarify the text. For example, a Calvinist might quote Ephesians 1:11 that God does “all things”. To show the Calvinist that “all things” does not have to mean “everything always”, 1 Corinthians 15:27 might be used in which Paul clarifies that “all things” does not include Jesus. The point is that in normal human communication, “all things” is limited to the context and doesn’t have to mean “everything always”. Although it does not “prove” that “all things” in Ephesians 1:11 does not mean “everything always” it does prove that “all things” does not have to mean “everything always”.
This shows the Calvinist that it is not unreasonable to believe something else about their proof text. It illustrates.
So what is the difference between using illustrations and obfuscation? How can we know whether someone is trying to obfuscate or illustrate?
The main “tell” is if the other person’s additional text clarifies or complicates the original text. If the person’s narrative complicates the text, they most likely have a strategy of trying to make people ignore the text due to the implications of the text. They are obfuscating. If the person’s narrative clarifies the text (makes the events easier to understand in context), then they are more likely using an illustration.
A second “tell” is if the person is actively trying to return the conversation to the original text. Someone who obfuscates will be very hesitant to try to refocus the conversation on the original text. Their entire point of pulling in other considerations was to detract and distract from the text. They will not use their other sources to clarify the original text. On the other hand, if someone is actively trying to return the conversation to the original text, then they are clarifying or illustrating.
A third “tell”, and maybe the most important, is if the clarification actually answers an objection by critics. It could be the case that the additional verses do not even speak to the original objection. If two children were having a debate over a box of cereal, one child may be arguing that the box is filled with Cheerios although the outside of the box says it is Lucky Charms. If the second child was to argue that it was not filled with Cheerios because every previous box of Lucky Charms he ever opened was filled with Lucky Charms, then this does not even address the original contention. It is a non-issue. So if one person claims that the “men from Judea” in Acts 15 considered themselves Christians, were disciples of the 12 apostles, and under the authority of the 12 disciples (arguing that they up-channeled the matter to the 12 disciples for resolution), then a proper response is not: “They were heretics because they preached something different than the 12 disciples”. That response ignores the original point.
When debating people, it is important to watch their strategies. Obfuscation is just one sign of intellectual dishonesty.