Government
Explanation
The Joke
A group of people are debating what the ideal form of government is. One person suggests it should be "the one that brings the most happiness." Another points out that this depends on a lot of things -- culture, history, technology, geography -- making it nearly impossible to determine which system is truly best. A third person then makes a logical leap: since we cannot know what brings the most happiness, we should logically just choose whichever form of government has the funniest name.
The final panel shows someone asking "What's it going to be?" and the answer is "A Dong" -- apparently the name of some governmental system selected purely for its comedic value.
The Humor
The comic satirizes political philosophy debates by exposing how they often reach an impasse: if the "best" government depends on countless variables that are impossible to fully account for, then the entire exercise of debating ideal government structures becomes somewhat futile. The joke takes this to its absurd conclusion -- if we truly cannot determine the best system by rational analysis, then we might as well pick the one with the funniest name. This is a classic SMBC move of taking a legitimate intellectual question, following it to an absurd but technically logical conclusion, and landing on something juvenile (a name that sounds like a body part).