In Forrester v. Rauland-Borg Corp., Judge Posner debunks dicta from employment discrimination cases to the effect that an employer's profferred non-discriminatory reason for the employment action against the plaintiff cannot be disproved by evidence or argument that it was "insufficient to motivate" the action.
Judge Posner explains:
"If it was insufficient to motivate the action, either this means that it didn’t motivate it, or that it shouldn’t have motivated it. If the first is the intended sense, the dictum is just a murky way of saying that the stated reason was not the real reason. If the second sense is the one intended, then the dictum is wrong because the question is never whether the employer was mistaken, cruel, unethical, out of his head, or downright irrational in taking the action for the stated reason, but simply whether the stated reason was his reason: not a good reason, but the true reason."