Much of Heiser's work focused on the Biblical and Old Testament view of the "Unseen Realm": a supernatural world, distinct from the physical realm, inhabited by hierarchical order of spiritual beings, like angels, demons, and a
divine council.
Kevin Bauder of the
Central Baptist Theological Seminary of Minneapolis called Heiser the "most prominent evangelical defender" of the divine council interpretation of
Psalm 82, and said that Heiser "has become a[n]... evangelist for the divine council theory, giving it wide exposure in popular books and articles, and defending it" through his blogging and other internet activities.
Criticism of ancient astronaut arguments Heiser spoke out critically against proponents of pseudoscientific
ancient astronaut conjectures, especially as popularized by
Zechariah Sitchin. Heiser appeared in
Ancient Aliens Debunked as an expert on the
Hebrew Bible and Ancient Near Eastern texts. ==Career==