The following argument is valid or forceful. Identify the irrelevant premise: If Tokugawa Ieyasu had not triumphed at the Battle of Sekigahara, Japan would not have been subject to the Shogunate for over 250 years until the Meiji Restoration of 1868. But the Shogunate did rule Japan for that long, so he must have won that battle. But Ieyasu would not have won if several of the opposing generals had not changed sides during the battle.
A) The Tokugawa Shogunate ruled Japan for over 250 years.
B) Ieyasu would not have won the Battle of Sekigahara if several of the opposing generals had not changed sides during the battle.
C) If Ieyasu had not won at Sekigahara, Japan would have not been subject to the Shogunate for over 250 years.
D) Ieyasu won the Battle of Sekigahara.

Question

Quizplus · Accepted Answer

The irrelevant premise is "But the Shogunate did rule Japan for that long, so he must have won that battle." This premise does not contribute to the logical validity of the argument, as the conclusion is based on the premise that Ieyasu would not have won the battle without the opposing generals changing sides, not on the fact that the Shogunate ruled Japan for a long time.

The Following Argument Is Valid or Forceful