We are not allowed, according to Halacha, to give directions by saying “go up the road of Zeus, and take a right at the Temple of Aphrodite.” The language of avodah zorah must not be part of our speech.
Yet this week’s sedra, has Hashem telling Moshe to turn the people back to camp between “Pi-HaChiros” and “Baal-Zephon.” The former means shrines of Horus (a major Egyptian deity), and Baal-Zephon, a version of Baal, a common Phoenician and Canaanite name for deities. How can the Torah give directions using foreign deities? We have never shrunk from renaming places before; the location of yetzias mizrayim could have been given using other landmarks, or other names for the same landmark.
The events up to and including the exodus from Egypt were the introduction of Hashem to the rest of the world. Never before had Hashem appeared on the world stage – he was the god of Avraham, or Isaac, or Jacob – in a polytheistic world, he would have been seen as a familial, or perhaps a tribal deity, not as a world power, so to speak. Indeed, unlike all the other deities, Hashem had no shrines, no physical representations – what proof was there that he existed? When Moshe first comes to Pharoah and asks him to let the Jews go, Pharoah asks “Who is Hashem… I do not know Hashem.” This is more than a statement that Hashem has no authority in Egypt; it is genuine confusion. The ancient world tracked their deities carefully, and Hashem was not found in the database. Moshe’s reply, that Hashem is “The G-d of the Hebrews,” was an attempt to help locate Hashem in Pharoah’s Deity Database, and allow Pharoah to save face and let the Jews go.
The deliverance from Egypt was Hashem’s “coming out party.” And Hashem’s emergence on the world stage, with the unique claim to be greater than deities they worshipped. Rabbi Chaim Leib Shmuelevitz has explained that if enough people worship a stick, that stick can perform miracles. People are given, by Hashem, the power to create, both in words and deeds, so the worship of invented deities has imbued those deities with power. They exist and have some kind of reality, because all other deities, had two audiences: people, and the people worship them.
The answer to our question is found in the Song: “Mi Chamocah BaElim Hashem,” “Who can compare to you among the deities, Hashem!” G-d has demonstrated his unique superiority over all the other deities. That is achieved by demonstrating, for the Jewish people, that G-d triumphs over the foreign gods. And it is achieved by proving, to the deities themselves, that they have been bested by Hashem, the One G-d. The two foreign deities “present” at the Exodus are bearing witness to the destruction of Pharoah and the superiority of Hashem. Nobody can compare to you, Oh Hashem!
At the Exodus, Pharoah is killed. Pharoah is considered to be the human form of Horus – the very deity whose shrine overlooks the Red Sea. Horus is no minor deity; he is considered the patron deity of all of Egypt. Hashem’s triumph over Pharoah is a direct statement: Hashem is more powerful than Egypt herself. And Baal Zephon (merging semitic Baal with Greek Zephyros to mean power of the west wind) is the deity of Phoenician lands to the East and North of Egypt, so the second divine witness is the G-d of the neighboring lands. There is one witness from each land. The victory does not establish Hashem only as superior in the pantheon to Egypt’s gods, but also to any deity in the region.
This ties in nicely with the interpretations that the Ten Plagues were each meant to demonstrate Hashem’s superiority over the Egyptian deities: the Nile river in the plague of Blood, for example, or Ra, the sun G-d, in the plague of Darkness. Yetzias Mizrayim, and the complete annihilation of Pharoah, makes the emphatic case for Hashem as the One and True G-d, witnessed by man and deities alike.
This then answers the initial question: we cannot use the names of foreign deities when giving directions because such a use imbues them with meaning, or even authority. The Torah uses the names of foreign deities for the opposite purpose: that Horus was powerless to stop the ignominious death of his corporal being, Pharoah, shows the complete superiority of Hashem.
Note: For a more normative interpretation, see the daas zekanim on the pasuk and/or samach hil avodah zarah perek heh halacha yud aleph