Deuteronomy 6.4-9, also known as the Shema because the first word of the passage in Hebrew is the imperative shĕma‘, meaning “Listen,” is probably one of the most well known passages in all of biblical literature. In Jewish tradition this passage is frequently recited as a prayer, a practice that goes back at least to the early rabbinic period . The broader Judeo-Christian tradition, moreover, has often taken the first verse of this passage as a statement of Israel’s (and its own) radical monotheistic faith. This verse reads: “Listen, O Israel, Yahweh is our God, Yahweh is one.” However, this common Judeo-Christian interpretation which claims that Israel maintained a radical monotheistic stance, or a belief that there is only one G/god in existence (in this case, Yahweh, the God of Israel), has been subject to severe criticism by modern biblical scholars.
The book of Deuteronomy is a significant section of the Pentateuch. However, unlike the rest of the Pentateuch which was redacted together primarily from the sources known by scholars as J, E, and P (as well as a number of other smaller sources), modern biblical scholars believe, for a number of linguistic, literary, and source-critical reasons, that the book of Deuteronomy constitutes a separate source, which is known easily enough as the D source since this source is located almost exclusively in the book of Deuteronomy.  Most biblical scholars connect at least some part of this source with the book that was discovered in the Temple sometime in the late seventh century during King Josiah’s reign in 2 Kings 22.8, as Josiah’s religious reforms align remarkably well with certain fundamental concepts and laws that are emphasized repeatedly throughout Deuteronomy (of course, it should be noted, that the author(s) of the book of Deuteronomy undoubtedly made use of other earlier sources and traditions).  For instance, like Josiah’s reforms, Deuteronomy emphasizes that it is Israel’s duty according to the covenant that Yahweh made with their ancestors to worship him exclusively and to do so only at the central sanctuary (presumably in Jerusalem).
In establishing the socio-historical context of the book of Deuteronomy, modern biblical scholars have perhaps most profitably compared Deuteronomy’s rhetorical style and literary structure to ancient Near Eastern treaty texts, and especially those of the Hittites and Assyrians.  A number of these ancient Near Eastern treaty texts have been recovered documenting a conquered ruler’s politically aligning himself as a vassal to a superior foreign overlord. These treaties are termed “suzerainty treaties,” since the treaties were typically entered into by two kings or states of unequal status—namely, the superior king, termed the suzerain, and the dependent or client king, known as the vassal. These treaties had a number of stereotypical features, known as the covenant formulary by some scholars, and used specific technical terminology. For instance, many of these ancient treaty texts begin with a preamble in which the suzerain identifies himself. Then follows a historical prologue in which a recitation of the past history between the two parties is recounted. Thereafter follows the treaty’s terms of agreement, known as the stipulations; these stipulations are usually in the nature of direct address in the second person. In these treaties there is usually also a stipulation for the preservation of the text, which stipulation sometimes required the text at certain times to be publicly recited. Moreover, the treaties usually have a list of witnesses, often of the patron gods of the two kings before whom the covenant oath is sworn, but sometimes the witnesses also included elements of nature, such as the heavens and the earth, the mountains, or rivers. Finally, these suzerain treaties would often conclude with a section detailing the blessings and the curses that would occur if the treaty was broken. The purpose of suzerainty treaties was to secure the complete loyalty and fidelity of the vassal to the suzerain economically, politically, and militarily. Modern scholars have convincingly pointed out many of these covenant formulary features in Deuteronomy, and it seems clear, based on these parallels as well as Deuteronomy’s terminology, that the text overall should be read, as Marc Brettler has stated, as a “theologized treaty—in which God is the overlord and Israel is the vassal…Deuteronomy is the religious transformation of a political document.” 
The literary and historical context of Deuteronomy described above, I believe, is significant for the purposes of analyzing the first verse of the Shema. First, the Shema must be seen as part of the Deuternomistic agenda to secure the worship of Yahweh alone at the central sanctuary. All other worship is expressly prohibited. This agenda, for instance, largely explains why the kings of Israel (i.e., the northern kingdom) were so vociferously condemned, even though it is most probable that Yahweh was worshiped at the proscribed sites of Dan in the north and Bethel in the south. Further, the Shema is part of a larger treaty (or covenant) context, the purpose of which is to secure Israel’s allegiance to Yahweh alone (and, as mentioned, in one centralized location).
Given this context, then, what does this passage probably mean? It means that Yahweh alone among the gods, and only as manifested in Jerusalem, is supreme and has total claim to Israel’s loyalty and worship; As Richard Nelson notes concerning this passage in his commentary of Deuteronomy, “Unlike Baal, who was manifested at scores of local high places around the country, the one true God has only one true place of worship.”  There is only one God for Israel. As Carl Ehrlich has stated:
“Hear, o Israel! Yhwh is our god, only Yhwh (or: Yhwh is one)” (Deut 6:4). This verse, which has been understood as the Jewish equivalent of the first part of the Muslim shahadah (“There is no god but God [= Allah], and Muhammad is his prophet”), namely as an absolute monotheistic declaration, can also be read in context as a henotheistic statement: Among the gods, Yhwh is the one whom Israel is to worship, but he is not the only god there is. If one translates the last phrase of the so-called Shema (“Hear”) as “Yhwh is one,” then the implication—in accord with the common scholarly dating of this text to the time of the religious reform of King Josiah of Judah in the late seventh century BCE (see Sweeney 2001)—is that one is to worship Yhwh only in his manifestation as god in Jerusalem and not in his various other local manifestations. In neither of the above passages [referring also to Exodus 15.11] is there any clearly monotheistic intent.” 
The statement, therefore, that Yahweh is “one” is not to be read anachronistically as an ontological statement of his nature in the abstract, but rather as part of Deuteronomy’s overarching concern that according to the Mosaic covenant Israel exclusively worship Yahweh at his one appointed place, namely the temple in Jerusalem; the passage, when situated properly in its historical context in Israel specifically and in the broader ancient Near Eastern world more generally, is concerned with a covenant relationship and its attendant obligations. It is not about metaphysics or abstract philosophical statements concerning God’s ontological nature.
Thus the Shema may be seen as consistent with numerous other biblical passages which clearly state or imply that there are other real gods in existence, although Yahweh is seen as supreme among them. For instance, Exodus 15.11 (NRSV, adapted) reads, “Who is like you, O Yahweh, among the gods? Who is like you, majestic in holiness, awesome in splendor, doing wonders?” (Compare also the following Old Babylonian hymn to the moon god Sin: “Lord, who surpasses thee? Who can equal thee? Great hero, who surpasses thee? Who can equal thee? Lord Nanna, who surpasses thee? Who can equal thee?” ) Psalm 95.3 (NRSV, adapted) says, “For Yahweh is a great God, and a great King above all gods.” Psalm 82.1 and 6 read, “God stands in the divine council, among the gods he judges…I have said, ‘you are gods, all of you children of the Most High’.” Thus, the God of Israel is the Most High (God) because there are other, subordinate gods in his heavenly council. Psalm 29.1 (NRSV, adapted) further states, “Ascribe to the Yahweh, O sons of God, ascribe to Yahweh glory and strength.” Moreover, Psalm 89.6 (NRSV, adapted) reads, “For who in the skies can be compared to Yahweh? Who among the sons of God is like Yahweh…?” Psalm 99.2 (4QPsalm) declares, “Yahweh is great in Zion, he is exalted over all the gods.” Additionally, Deuteronomy 32.8-9 states that gods were appointed to rule over other nations just as Yahweh was appointed to rule over Israel. This text reads, “When the Most High apportioned the nations, when he divided humankind, he fixed the boundaries of the peoples, according to the number of the gods. Yahweh’s portion is his people, Jacob his allotted share.” Furthermore, Deuteronomy 32.43 (NRSV) goes on to affirm that, “Praise, O heavens, his people, worship him, all you gods!” Finally, Job 38.4-7 (cf. Genesis 1.26-27; 3.22) (NRSV, adapted) states: “Where were you when I laid the foundation of the earth? Tell me, if you have understanding. Who determined its measurements—surely you know! Or who stretched the line upon it? On what were its bases sunk, or who laid its cornerstone when the morning stars sang together and all the sons of God shouted for joy?” This is just a sample of biblical texts that demonstrate that the biblical authors believed that there were other gods besides Yahweh in existence. (This fact, in turn, helps make sense of Deuteronomy’s desire to secure Israel’s allegiance to Yahweh alone, since if it was held generally in Israel that these other gods were not actually real there would be no need to argue so passionately for allegience to Yahweh alone.)
What, then, does all of this mean for those who desire to claim that ancient Israel (and the Bible in general) affirmed a radical monotheistic belief? As noted biblical scholars Cyrus Gordon and Gary Rendsburg comment after discussing biblical tradition regarding the crossing of the Sea of Reeds:
“The story is told not only in prose (Exodus 14), but it is celebrated in song as well (Exodus 15). It is important to note that at this time God is recognized as the supreme but not the only god. The query in the Song of the Sea, “Who is like You among the gods, O Yahwe?” (Exodus 15:11), indicates that God is beyond compare but is not the only deity. Also in the Ten Commandments (Exodus 20:2-17) it is said, “You shall not have other gods before Me…You shall not bow down to them or worship them because I, Yahwe, your God, am a jealous God.” And above we noted that the Bible understands the ten plagues as attacks on Egyptian deities. Throughout most of the Hebrew Bible, the existence of other gods is recognized, but their worship is forbidden.” 
Finally, I close with the following quote from Harvard’s Jon Levenson:
“A hymn does not speak in the same language as a philosophical treatise. Thus, most of the statements of the uniqueness or kingship of YHWH are actually affirmations of his incomparability; they tend to occur in a context of hymnody…Israel did not assert the oneness of her God with the dispassion of a philosopher. She praised God for being unique, incomparable, a source of embarrassment to his rivals, their master…[Moreover,] The hymnic affirmation of the incomparability of YHWH has been found to be paralleled nicely in other literature of the ancient Near East.”
 See Marc Z. Brettler’s book How to Read the Jewish Bible (New York, NY: Oxford University Press, 2007), page 92. However, as Professor Brettler notes on page 305, note 24, in its historical context this passage was not actually a prayer.
 Michael D. Coogan, The Old Testament: A Historical and Literary Introduction to the Hebrew Scriptures (New York, NY: Oxford University Press, 2006), pages 92, 26-27, and 173-177.
 For what follows in this paragraph, see Michael D. Coogan, The Old Testament: A Historical and Literary Introduction to the Hebrew Scriptures (New York, NY: Oxford University Press, 2006), pages181-183; Marc Z. Brettler, How to Read the Jewish Bible (New York, NY: Oxford University Press, 2007), pages 90-92; Jon D. Levenson, Sinai & Zion: An Entry into the Jewish Bible (New York, NY: HarperCollins Publishers, 1987), pages 26-36.
 Marc Z. Brettler, How to Read the Jewish Bible (New York, NY: Oxford University Press, 2007), page 93.
 See page 197 of Richard D. Nelson’s commentary on Deuteronomy in The HarperCollins Bible Commentary (New York, NY: HarperCollins Publishers, Inc., 1988), edited by James L. Mays.
 See pages 321-322 from Carl S. Ehrlich’s article “Hebrew/Israelite Literature” in the volume From an Antique Land: An Introduction to Ancient Near Eastern Literature (Lanham, Maryland: Rowman and Littlefield Publishers, Inc., 2009), edited by Carl S. Ehrlich.
 Cyrus H. Gordon and Gary A. Rendsburg, The Bible and the Ancient Near East (New York, NY: W.W. Norton & Company), pages 148-149.