The grass is wet because the sprinkler is on The grass is wet because it's raining The grass is wet The grass is wet because the sprinkler is on The grass is wet because it's raining The grass is wet It's cloudy, so the sprinkler is off Two extensions: either because it's raining, or because the sprinkler is on. One extension: because it's raining. we simply accept the grass is wet... Dung, Phan Minh. "On the acceptability of arguments and its fundamental role in nonmonotonic reasoning, logic programming and n-person games." Artificial intelligence 77, no. 2 (1995): 321-357. Argumentation is about consistency rather than truth, so arguments are acceptable or not. A set of arguments that are acceptable together is called an extension. An argument is acceptable if it isn't attacked, or if it's defended by an attack on its attacker. With arguments as nodes, attacks as edges, we can draw a directed graph: Why is the grass wet? DOI: 10.1016/0004-3702(94)00041-X ASPIC+ AIF