As a rule, we don’t like to feel to sad or lonely or depressed. So why do we like music (or books or movies) that evoke in us those same negative emotions? Why do we choose to experience in art the very feelings we avoid in real life?Aristotle deals with a similar question in his analysis of tragedy. Tragedy, after all, is pretty gruesome. […] There’s Sophocles’s Oedipus, who blinds himself after learning that he has killed his father and slept with his mother. Why would anyone watch this stuff? Wouldn’t it be sick to enjoy watching it? […] Tragedy’s pleasure doesn’t make us feel “good” in any straightforward sense. On the contrary, Aristotle says, the real goal of tragedy is to evoke pity and fear in the audience. Now, to speak of the pleasure of pity and fear is almost oxymoronic. But the point of bringing about these emotions is to achieve catharsis of them – a cleansing, a purification, a purging, or release. Catharsis is at the core of tragedy’s appeal.
Brandon W. Forbes, Radiohead and Philosophy: Fitter Happier More Deductive