Paul wrote of beings existing "under the earth." Paul's Hellenistic and Jewish readers were familiar with underworlds in which beings lived, i.e., the Greek Hades, the Roman Tartarus (both terms appearing in the Gospels themselves) and the shadowy Sheol of the Hebrew Bible:
The departed spirits tremble under the waters and their inhabitants. Naked is Sheol before Him [Yahweh].A witch in Endor calls up Samuel from Sheol. (She is not calling him up from his personal burial site because he was not buried in Endor.) 1 Sam. 28:3,12ff
The dead are not simply lying dead in the earth but "under the earth" and remaining active in some sense, if only in a shadowy sense in the case of early Greek and Hebrew views of Hades and Sheol. Below are verses from Paul and Revelation that mention beings living under the earth. Consider them from the viewpoint of a first century Hellenistic convert:
That at the name of Jesus every knee should bow, in heaven and on earth and under the earth.English Bibles fail to render fully the meaning of "under the earth" in the above verse--the Greek word katachthonion refers to “the beings down (kata) in the chthonic (chthovios) or subterranean world.” The Anchor Bible translation is "those in the world below," with the added comment, "katachthonioi was a designation for the dead in the underworld [the commentary then cites sources from Hellenistic antiquity]. . . The meaning is spirits above, humans on earth, and the dead in Hades, appropriate for 'the Roman milieu of Philippi.' . . . The full phrase came naturally for Christians there to describe the universe. . . Those in the heavens [several 'layers,' 2 Cor. 12:2 'the third heaven']; on earth [1 Cor 8:5; 10:26; 15:47]; and in the world below, Sheol or Hades." [John Reumann, Philippians, The Anchor Yale Bible, 2008, p. 357-58]
The book of Revelation features a similar notion:
No one in heaven or on earth or under the earth could open the scroll or even look inside it. Revelation 5:3 . . . Then I heard every creature in heaven and on earth and under the earth and on the sea, and all that is in them, singing: "To him who sits on the throne and to the Lamb be praise and honor and glory and power, for ever and ever!" Revelation 5:13Also consider how a Hellenistic convert might read these verses, starting with talk of a "prince of the power of the air," and also about "descending into the lower parts of the earth":
. . . in which you formerly walked according to the course of this world, according to the prince of the power of the air, of the spirit that is now working in the sons of disobedience. Ephesians 2:2 . . . That the manifold wisdom of God might now be made known through the church to the rulers and the authorities in the heavenly places. Ephesians 3:10 . . . Now this expression, "He ascended," what does it mean except that He also had descended into the lower parts of the earth? He who descended is Himself also He who ascended far above all the heavens, so that He might fill all things. Ephesians 4:9–10 . . . Our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places. Ephesians 6:12Interestingly, a different letter says that these "things in heavenly places" were reconciled to God:
. . . and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross.FURTHER INFORMATION ON SHEOL IN THE OT
Sheol is typically depicted as a place to which one "goes down" (urd; see Num 16:30;Job 7:9; Isa 57:9; cf. Isa 29:4; Ps 88:3-4). It represents the lowest place imaginable (Deut 32:33; Isa 7:11) often used in contrast with the highest heavens (Amos 9:2; Ps 139:8; Job 11:8). To emphasize further the depth of Sheol we also find it modified by tahtit/tahtiyyot (e.g. Deut 32:22; Ps 86:13; Ezek 31:14-18), usually translated "the lowest parts of the underworld."
Sheol is also associated with terms for chaotic waters, including Sea, River, breakers, waves, and the deep. So Sheol is associated with primeval waters lying beneath the earth as well as with judgmental waters loosed by God (water that God is depicted elsewhere as miraculously holding back in order to maintain creation, see "The Cosmology of the Bible" chapter in The Christian Delusion). Ancient Near Eastern imagery also links a crossing of water with one's travel to the underworld and the imagery is so common from Mesopotamia to Greece that it probably played a role in the Hebrew linkage of water with the land of the dead.
The inhabitants of Sheol are called the Rephaim, and a great deal of literature has been written on the nature of the Rephaim since the publication of Ugaritic texts where they are mentioned extensively.
As already stated, it is not a matter of being forced to choose between totally metaphorical usage versus all other usages or understandings. In early usage Sheol is like a metaphor for the Uber-grave, but even metaphors do not preclude other meanings, depictions, definitions rather than purely "burial imagery." In fact, recognition of ideas shared by biblical and ANE sources makes the likelihood of belief in a three-tier cosmos more likely, not less so. Same goes for NT conceptions, see below.
FURTHER INFORMATION ON THE UNDERWORLD IN THE NT
The underworld is depicted not only as "Hades" in the NT (into which Christ descended in order to preach to the spirits of the dead, 1 Pet 3:18-20; 4:6--such a "descent into hell" becoming part of the Apostle's Creed), but the underworld is also depicted as the "Abyss" (abussos), often translated as "Bottomless Pit" (Luke 8:31; Rom 10:7; Rev 9:1-2,11; 11:17; 17:18; 20:1,3). "Tartarus" is another word derived from Greek mythology and employed by NT authors, it's a place that Greeks depicted as lying as far below Hades as earth is below the heavens, so much so that an anvil could fall for nine days and nights until it reached it. Tartarus is described as a prison with gates and sometimes personified (as was Hades, and also Sheol in the OT). The author of 2 Peter 2:4 mentions rebel angels being cast into Tartarus, based on a story found in the inter-testamental work, 1 Enoch (or at least based on a general knowledge of the "Watchers" myth in 1 Enoch):
1 Enoch 10:2-3, 10:11-14 -- A deluge [Flood] is about to come upon the whole earth . . . And the Lord said unto Michael: 'Go, bind [the evil angels] in the valleys of the earth till the day of their judgment . . . is consummated. In those days they shall be led out to the abyss of fire: and to the torment and the prison in which they shall be confined for ever.
Compare 2nd Peter 2:4-5 -- God spared not angels when they sinned, but cast them down to hell, and committed them to pits of darkness [Tartarus], to be reserved unto judgment; and spared not the ancient world, but preserved Noah . . when he brought a flood . . .
Portions of the Book of Enoch can also be found in the NT books of Jude and Revelation. Interestingly, 1 Enoch depicts a flat earth.
[Much of the information in the above sections on Sheol and the NT underworld was derived from Theodore J. Lewis, "Dead, Abode of the," Anchor Bible Dictionary, Vol. 2, Doubleday, 1992]
FINAL POINT OF INTEREST: DID THE ANCIENT ISRAELITES VIEW SHEOL AS REAL OR NOT?
"A cursory overview of modern interpretation of biblical thanatology quickly reveals the lack of current consensus among scholars. There is pressing need for further study and clarification. Was Sheol real or not for ancient Israelites? If it was real, were all souls expected to end up imprisoned there? How did Israelites interact (or refrain from interacting) with the shades of the dead?"--Stephen L. Cook
Cook's complete paper is online: Funerary Practices and Afterlife Expectations in Ancient Israel
Prior to the publication of his paper Stephen L. Cook also composed these shortened presentations of various points:
To Be Gathered To One's People
Burial and Afterlife in Yahwism, Part 2
Burial and Afterlife in Yahwism, Part 3
Burial and Afterlife in Yahwism, Part 4
Burial and the Hereafter in Yahwism, Part 5
Burial and the Hereafter in Yahwism, Part 6
Yahwism and Life after Death: Part 7
Life after Death, Part 8
See also this new book on the afterlife, L’homme face à la mort au royaume de Juda: Rites, pratiques et représentations by Hélene Nutkowicz. Cook comments: "Nutkowicz suggests that the Hebrew people believed in amortality. At first glance, it seems to me that this might be a helpful term, since it stresses that the soul does survive death, but it does not view death as positive or beatific as might be implied by the term immortality. N. also discusses the relationships between the living and the dead, the repa’im [also spelled, Rephaim], the ’elohim, the practice of necromancy, the duties toward the dead and toward the living, inscriptions, and the cult of the dead and of the ancestors."