With a favorite Firing Line guest, a serious discussion of the nature of angels and what Mr. Adler calls "angelistic fallacies." An angel, he points out, is "a purely spiritual being, a mind without a body"; he quotes Thomas Aquinas's explanation that angels must assume a body to appear on earth--"as you would assume a coat or a mask when you go to a masquerade ball"--"because they must make a sensible appearance to the human beings that they are carrying God's messages to."