A proto-pluralistic midrash

הה"ד: (דברים ד) השמע עם קול אלהים.

המינין שאלו את ר' שמלאי:

א"ל: אלוהות הרבה יש בעולם?

אמר להם: למה?

אמרו לו: שהרי כתיב: השמע עם קול אלהים!

אמר להם: שמא כתוב מדברים אלא מדבר.

אמרו לו תלמידיו: רבי לאלו דחית בקנה רצוץ, לנו מה אתה משיב?

חזר ר' לוי ופירשה:

אמר להם: השמע עם קול אלהים, כיצד?

אילו היה כתוב קול ה' בכחו לא היה העולם יכול לעמוד, אלא קול ה' בכח, בכח של כל אחד ואחד.

הבחורים לפי כחן,

והזקנים לפי כחן,

והקטנים לפי כחן.

אמר הקב"ה לישראל: לא בשביל ששמעתם קולות הרבה תהיו סבורין שמא אלוהות הרבה יש בשמים, אלא תהיו יודעים 

שאני הוא ה' אלהיך, שנאמר: (שם ה) אנכי ה' אלהיך.

I don't think the Sages were pluralists, and I don't think they subscribed to modern ideas about our subjective, and therefore inevitably fallible perception. Still, its hard for me, a man of 2010, to read this midrash (its recorded in Shmos Raba 29:1) without remembering Isiah Berlin, and what he taught about human understanding. Here it is in translation:

The sectarians challenged Rav Samlai: "There are many Gods in the world, as it is written: השמע עם קול אלהים [The nation heard the voice of God. The word for God - Elohim - is plural]." Rav Samlai replied: [Elsewhere the verb attached to Elohim is singular, proving the word Elohim is to be understood in the singular.] Rav Samlai's students said, "Teacher, you defeated the sectarians with [a weak argument]. What will you tell us?"

Rav Levi expounded: "How shall we understand the phrase, The nation heard the voice of God?" In Psalms we have a verse, which doesn't read: קול ה' בכחו [the voice of God is his power] for if that were true the word couldn't have stood [when God spoke.] Rather, the verse in Pslams reads קול ה' בכח [the voice of God in (or with) power] meaning, that the voice of God comes according to the power of each of us.

To the young people according to their power [of understanding]
To the old people according to their power [of understanding]
To the children according to their power [of understanding]

[The verse the sectarians originally mentioned should be understood as if] God says to Israel "Though, you heard many voices [i.e. your subjective powers of understanding led to different conclusions] don't let yourself become convinced that there is more than one God; always know that I am the Lord your God. [i.e. I am one]

How does a pluralist understand this midrash? First, it serves as a reminder that human beings perceive things differently. That's a function of our humanity. Each of us are different, and each of us relate differently to the world. Some understand God one way, others see Him and understand His demands in another way.  Second, the midrash, as I read it,  seems to say that so long as we remember that there is one God, a phrase Rav Levi meant symbolically, these different perceptions are valid.

The pluralist, to quote Issiah Berlin, holds that "that there is a plurality of values which men can and do seek." This collection of human values men seek isn't infinite, and its possible to pursue your own preferred values, while also detesting a set of values held by someone else -- and even going to war with it. Pluralism, unlike relativism, objects to the notion that "anything goes"; rather,  it simply recognizes that men can and do pursue many different sets of values, and that these difference value sets aren't necessarily hostile to one another.

Though the Sages certainly would have disapproved of Jews who ate pork or violated Shabbos, this midrash suggests that there was some room in their imagination for legitimate diversity, i.e. for Jews to legitimately pursue different values.

This is a welcome reprieve from the one-size-fits all style of Orthodox Judaism with which we contend today.

Berlin also says: "If.. respect between systems of values which are not necessarily hostile to each other is possible, then toleration and liberal consequences follow, as they do not either from monism (only one set of values is true, all the others are false) or from relativism (my values are mine, yours are yours, and if we clash, too bad, neither of us can claim to be right)."

It seems possible (at least according to Rav Levi)  that when two Jews to subscribe to different value sets, this diversity can be tolerated, so long as the different value sets are not inherently hostile to each other, i.e. so long as both value sets are included in whatever Rav Levi beleives is indicated by the words, "I am the Lord your God."