Philosopher: It is absurd to argue that people are morally obligated to act in a certain way simply because not acting in that way would be unnatural. An unnatural action is either a violation of the laws of nature or a statistical anomaly. There is no possibility of acting as one cannot, nor does the mere fact that something is not usually done provide any good reason not to do it. Which one of the following most accurately describes a technique used in the philosopher's argument? ['stating the definition of a key term of the argument', 'using statistical findings to dispute a claim', 'using empirical evidence to support one definition of a key term of the argument over another', 'undermining a claim by showing that the claim is self-contradictory']