What does Daniel 2:4 mean?

In this context, "Chaldeans" are astrologers and scholars associated with the Babylonian Empire. Their king, Nebuchadnezzar, made an unusual and impossible request. He wants their wisdom about a disturbing recurring dream (Daniel 2:1–3). Yet he also wants them—the advisors—to tell him what he dreamed (Daniel 2:5). This appears to be a test; Nebuchadnezzar senses that this dream is too important to risk lies and invented predictions. If the self-proclaimed astrologers and occultists can't tell him what he dreamed, why think they have the insight to know what the dream means?

At this point, the book of Daniel changes languages: from Hebrew to Aramaic. The text will not return to Hebrew until chapter 8. The events of those passages are primarily messages to Gentile—non-Jewish—people. This includes the story of Shadrach, Meshach, and Abednego in the furnace (Daniel 3), Nebuchadnezzar's insanity (Daniel 4), the handwriting on the wall (Daniel 5), Daniel in the lions' den (Daniel 6), and Daniel's vision of the four beasts, which includes Messianic prophecy (Daniel 7). Each incident expresses the ultimate power and wisdom of the God of Israel. In that era, Aramaic was becoming the favored language of the Babylonian people. Recording these prophecies and miracles in the common language of a pagan people emphasized their obligation to learn from God's messengers.

When Sennacherib's messenger Rabshakeh threatened Jerusalem nearly a century prior, Jewish respondents asked him to speak to them in Aramaic. They understood Aramaic, but the residents of Jerusalem did not. The respondents did not want the people on the wall to understand what Rabshakeh threatened in the Hebrew language (2 Kings 18:26). At that time very few Jews knew Aramaic. Yet when their people returned to Jerusalem from the captivity in Babylon decades after this event with Nebuchadnezzar, Aramaic was common among the Jews. It could be that Nehemiah 8:8 is referring to language interpretation (explaining the Hebrew in Aramaic) and not just exegesis or teaching. In the first century AD, Aramaic was still common (John 19:20; 20:16; Mark 5:41).