When engaging in debate with an eye toward victory, that is, with the goal being to change your opponent's mind, the ideal circumstance is that each participant is able to engage on equal footing, supported by nothing but the strength of their own knowledge and arguments. However, this not always the case, and we can often find ourselves engaging in debate with someone who, by any of a number of means, possesses an advantage that bolsters them against the full force of our arguments, and may even allow them to emerge victorious even if our arguments appear stronger in isolation. These advantages serve as epistemological braces, providing a solid foundation to push off of even when an argument might not otherwise be able to stand on its own.
It is worthwhile to note that oftentimes, we do not necessarily debate for our own benefit, or even the benefit of our direct opponent(s), but for the benefit of those observing - the audience. Even if we fail to change the mind of the person debating opposite us, it is possible to change the minds of those who may be listening, and certain braces (particularly those of authority) can influence our audience just as much if not more than they can influence us.
I will note here that all of these braces exist independently of participants' weight class, and multiple braces can be present at time. Certainly, it may even be that both parties in a debate have access to such braces, though the honorable debater should do their best not to rely on them if at all possible.
This list is by no means exhaustive, but those braces noted here are fairly representative of the typical external factors that often influence the outcome of a debate.
By far the most common brace, authority comes in several different flavors:
Authority of credentials
A person with authority of credentials is what we most often think of when appealing to authority, and generally involves some kind of title denoting a certain level of education, or being a visible member of a specialized profession. However, much like with fallacious appeals to authority, these titles or professions do not necessarily equal legitimacy, hence why credentials are a brace rather than a component of weight class. This brace can be removed by arguing the strength of the credentials, though using this strategy can be dangerous given the fine line between legitimate questioning and ad hominem attack.
An individual with credentials will often dismiss their opponents' claims, whether internally or externally, if their opponent does not have similar credentials (or credentials that the individual chooses to recognize). Thus, this is the brace that most frequently shows up on both sides of a debate to establish the legitimacy of each party from the start.
Authority of arbitration
A person with authority of arbitration is, put simply, a person who has the literal power to decide who wins and loses a debate, exemplified (as one may expect) by an arbitrator or judge. Having the power to decide the outcome of a debate removes an enormous amount of pressure from the individual with that power, though directly engaging in debate with an individual with this authority tends to be rare. More frequently, those with authority of arbitration serve as an audience to a debate between third parties, declaring a winner at the debate's conclusion.
Authority of station
Authority of station tends to be more informal than the previous two entries, and is characterized by social authority of some kind. This can be anything from the authority of a parent over a child, a supervisor over an employee, or a teacher over a student (though a teacher would likely wield all three authorities in roughly equal measure when debating a student). Though there is some similarity to authority of arbitration here, the key difference is that there may be implied consequences unrelated to the debate once it has concluded, regardless of the debate's outcome.
Foundational assumptions can best be described as the set of premises an individual uses to define themselves at the most fundamental level. For example, a highly religious person might have "God exists" as a foundational assumption. By easy contrast, a particularly strident atheist may have "God does not exist" as one of their foundational assumptions. The brace lies in the fact that questioning these assumptions necessarily involves questioning the core of one's constructed identity, which is a difficult prospect even under the best of circumstances. When a debate begins to challenge an individual's foundational assumptions, it can become exponentially harder to present arguments that will change their mind, as such arguments attack their very sense of self. While it is of course entirely possible for people to enter into debate with a willingness to accept the strongest argument presented, regardless of its personal ramifications, such attitudes are rare even among more "enlightened" groups.
It can also be said that this is simultaneously both the strongest and weakest brace. While foundational assumptions are very good at preventing an individual from changing their mind and not losing, they aren't very good at convincing someone who doesn't already agree with them, and thus very rarely manage to help someone win an argument.
As noted previously, we don't always debate for the benefit of our opponent. Indeed, debate for the benefit of the audience is common, and even if you don't manage to convince your opponent, changing the minds of those who are watching can often be an alternative victory condition. That said, audience can itself be an epistemological brace, particularly when at least one participant has some level of public visibility.
Regardless of the mindset of the individuals actually engaging in direct debate, audiences are not always impartial. Just as we are wired on an individual level to instinctively reject evidence that conflicts with what we already believe, a group that starts out on the opposing side is more difficult to sway, both because of this individual behavior pattern, as well as through the exertion of peer pressure and threat of ostracism should anyone openly break from the status quo. Furthermore, depending on the venue and format of the debate, having a hostile audience might also mean having to argue against more than just one's primary opponent (or at the very least, needing to pointedly ignore people trying to insert themselves).
Note that "hostile" in this case does not necessarily imply any specific animus toward a participant. A hostile audience might instead have great admiration or reverence for one of the debate participants, which may affect how they engage with any arguments presented (whether for or against their side).
In some ways, having an uninformed audience is worse than having a hostile one. In this case, "uninformed" means not merely ignorant of certain specific facts or arguments that might be presented in the debate, but also lacking knowledge that would allow an audience member to independently evaluate the arguments presented. An uninformed audience relies on the debate participants for all of their information, and so they are particularly vulnerable to misinformation, as well various argumentative fallacies that might otherwise be unsuccessful in the face of more in-depth knowledge.
Uninformed audiences also have an alarming tendency to become hostile even during the course of a single debate, if one participant starts out particularly strong (as perceived by the audience). Once that attitude shift has occurred, you now face the double problem of a hostile audience that is also uninformed, which can be next to impossible to overcome in most circumstances.
There are occasionally times when we are not actually debating who we think we are debating. If we're able to recognize them, they become less "braces" and more "misdirections", but can be and are used as braces for as long as they go unnoticed or unchallenged.
Debating an Idea
Particularly in cases where pseudoscience or religion collide with established science, we actually end up debating against an idea or body of work, rather than an individual. A creationist arguing with an evolutionary scientist is not debating the scientist, not really. They're debating evolutionary theory itself. Discussing the merits of the Copenhagen interpretation or the many-worlds hypothesis with a staunch supporter of either is best characterized as engaging with the science, not with the person.
But how do we know when we're actually debating an idea? The best indicator that we're debating an idea is when the debate exhibits an arbitrarily high level of predictability. If the person arguing in favor of the idea being debated could, in theory, plop down a standard book about the idea in front of his opponent and accurately say "All of my objections can be found in here", then the other person is debating with an idea. This is not to say that debating an idea is bad, but that we should be careful to reframe or re-contextualize our arguments once we realize that's what we're doing. The other person ceases to matter, because all they are doing is waiting for us to make an argument, then picking out the preferred counterargument from an existing list. Ultimately, if we really are capable of calling a well-established idea into question, then back-and-forth, interpersonal debate is perhaps not the best venue to do so effectively.
Have you ever made a detailed, well-reasoned argument on the Internet, and then someone comes along, provides a link to an article written by someone else, and says "This person disagrees with you"? In so doing, that person has taken an ideological hostage. This should not be confused with simply using work from someone else as support for their own argument; rather, an ideological hostage occurs when the referenced work is used as the entirety of one's argument, without further elaboration, clarification, or synthesis. This tactic is easy to fall for, because we still feel like we're debating someone, but we're actually debating the person who wrote the referenced work, not the person who provided it. Worse, it can be very difficult to neutralize this brace, as asking for a summary in place of actually reading can lead to accusations of laziness or deflecting. The best method of engaging with this brace would be to ask probing questions to ascertain which parts the person specifically thinks supports their argument, but this also requires solid non-debate communication skills that not all debaters may have access to.
Epistemological braces are not logical fallacies (though they are often closely related), and they aren't inherently bad. Rather, they are something to be aware of when engaging in or observing a debate, because they allow us to identify what non-knowledge-based methods debate participants may be using to either bolster the strength of their own arguments, or deny the strength of their opponent's. In many cases, pointing out the existence of a brace can be counterproductive, as such a statement has a high probability of sounding like accusation and prompting defensiveness, so simple knowledge of and allowance for braces being present is usually the best method of minimizing their impact on a given discussion.