Theory is a style of debate focused around proving why a debater's practice is harmful in the debate round or debate in general. Typically, theory arguments will prove why a debater is being unfair or uneducational in the round. Although theory is intended to be used when your opponent is being unfair, abusive, or uneducational, it can be strategic more broadly by forcing your opponent to spend time answering your theory arguments, even if they were only marginally abusive. Theory is considered to come before and operate on a higher layer than substance, which means that even if you are losing the debate substantively but can successfully prove that your opponent is being unfair or uneducational, you would win the round.
Structure of a Shell
Theory (also called “theory shells” or just “shells”) are composed of four parts: the interpretation and violation, which isolates what your opponent is specifically doing that is unfair or uneducational, the standards, which proves how your opponent is being unfair or uneducational, and voters, which articulate why the judge should care about being fair or educational in round, among other things.
Click here for an in-depth guide on the structure of theory.
Since theory is initiated in response to abuse, it is commonly read in the 1NC or 1AR in response to something that your opponent has done. However, it can also be read preemptively in the 1AC to say that your opponent shouldn't do something in one of their future speeches. More rarely, it can be read in the 2NR in response to abuse from the 1AR.
Topicality is akin to a theory shell that proves the affirmative is not properly defending the resolution. If the affirmative reads a plan, the negative might read a topicality shell to prove both that it's unfair for the affirmative to not defend the entire resolution as stated and also that doing so is not consistent with the grammar of the resolution. T-Framework is read when the affirmative is not defending the resolution at all in the form of a non-topical affirmative.
Although one can read a theory shell about anything, certain theory shells that respond to common practices in debate are accordingly read more often. See the list of common theory shells for more. It's useful to know and drill against these common theory shells because they are likely to come up in many of your future rounds. Disclosure Theory is another common theory shell that is read to incentivize debaters to disclose on the HSLD wiki.
Although theory was originally intended to check back against legitimate abusive practices in-round, some debaters read theory arguments against practices that are not very abusive in the form of frivolous theory. Strategically, frivolous theory can be smart when theory is evaluated under an offense-defense paradigm. If your opponent wins that you are being even the tiniest bit abusive or that you aren't doing something that could make the round more fair, your opponent could win the round.
Combo Shells prove why some combination of arguments that your opponent is reading is abusive. Combo shells are often contextual to the given round and might be exempted on-the-spot. Combo shells are particularly strategic against tricky affirmatives that attempt to get you to concede some combination of arguments that causes you to lose the round.
Responding to Theory
Responding to Theory is an important skill to know as a debater, no matter your argumentative style.