You are not in your own home, intruder; you are a foreign body in the world, like a splinter in flesh, or a poacher in his lordship's forest. For the world is good; I made it according to my will, and I am Goodness. But you, Orestes, you have done evil, the very rocks and stones cry out against you.
In Act III, this is Jupiter's last-ditch attempt to bring Orestes back under the wing of his divine law. Having opposed the divine law of Good, Orestes has carried out Evil according to Jupiter. Jupiter created the entire world based on his divine laws of Good and Evil. The world itself is Good, and it is the world itself that rejects Orestes, who has not acted in accordance with its laws. The notion that human beings are foreigners in the world, thrown in among objects that are unlike them, is central to existentialism. The world, or Nature, acts according to scientifically discoverable laws. The movements of stars, wind currents, and tectonic plates follow the ordered rule of cause an effect. A stone will always fall if dropped, the sun will always come up the next morning, the trees will lose their leaves in autumn, and so on. Human bodies are also physical objects that follow the same laws as the rest of nature. Human consciousness, on the other hand, does not follow the laws of cause and effect; consciousness can examine the physical world and react to it, but these reactions are not definite ones. If I hit a pool ball at a particular angle and with a certain force, that pool ball will always go in the same direction. If, on the other hand, a pool ball hits me, my reaction will not always be the same and it might differ from any other person's reaction. While nature acts according to fixed laws, human consciousness creates its own laws. Human beings are thus fundamentally different from the world around them: they don't follow the same laws and as a result they are intruders.
Fixed moral systems like the one Jupiter instills are imposed on human beings from above. Members of a society are simply told how to act, and they are told that acting in this way makes them Good. Imposing moral laws on human societies brings people in line with the law-bound physical world around them. If I kill someone, according to the ruling moral law I must repent of my crime. Orestes has recognized his freedom: he does not have to follow the moral law because he can invent his own moral laws. Since Orestes does not act according to the fixed laws of nature or of the society of Argos, he has done evil. His free action is evil because it does not follow established laws. Freedom, then, is necessarily evil.