What is intended by describing Adam as "khalīfah"?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. Adam was the "trustee" of Allah in upholding His law, proclaiming the proofs of His Oneness, and judging among His creation. [Ibn Masʿūd, Mujāhid]
2. Adam was a "successor" to earlier created beings on Earth. [Ibn ʿAbbās, al-Ḥasan]