Pluralism is one of the obvious facts of the 21st century. But it is also a pressing challenge that modern societies, states and traditional religions have to recognize. Can religions and traditional societies accommodate diversity and pluralism? Or are they stuck in absolutism because of their insistence on theological and social unity?Comparing his philosophy with that of Hegel, German philosopher Ludwig Wittgenstein is reported to have said that while Hegel tries to show all differences to be the same, he sees all similarities as essentially different. According to Wittgenstein, Hegel sought to overcome differences to reach transcendental unity. He was so concerned with the absolute unity of things in philosophy and politics that he saw everything as evolving towards an eventual unity. He regarded history as marching towards a unity of the highest order. And he considered the unification of Germany as inevitable. But this yearning for the unity of all things turned Hegel's philosophy into an ideology of absolutism. By contrast, Wittgenstein's later philosophy sought to show everything as essentially different. In the Tractatus Logico-Philosophicus, he developed the famous "picture theory" whereby human language was thought to have mirrored reality as it is. An atomistic notion of reality led to an atomistic and one-dimensional concept of language. Logical positivism, which owes a lot the Tractatus, assumed a one-to-one correspondence between language and reality. Anything that was not expressed through logical symbols and propositions was declared meaningless. Wittgenstein had a life-changing experience and his later philosophy argued for an infinite complexity of the world. Human language expresses this complexity and variety in ways that go beyond logical atomism. Reality is too diverse, too complex and multilayered to be reduced to any one single formulation. What appears to be same or similar is at bottom different. The closest we can get is "family resemblance," i.e. familial traits shared by different members of a loosely connected group.Hegel's quest for absolute uniformism and Wittgenstein's radical philosophy of differences can be seen as two competing notions of unity and diversity. Both visions have had many followers. They produced absolutist ideologies and radical relativisms. On the one hand, there is the problem of religious, ethnic, sectarian and cultural absolutism, which suppresses freedom and human dignity. On the other hand, there is the issue of "anything-goes" relativism whereby the sense of interconnectedness, belonging and authenticity is lost.Striking a balance between unity and diversity may not be as easy as it seems. Emphasizing unity alone can lead to absolutism and exclusivism. Reliance on diversity alone can destroy common values and principles. Besides political ideologies, religions have been accused of imposing absolutism and suppressing diversity.It is true that religions offer a unified vision of reality and this makes them susceptible to absolutism. God is one and the reality which He created must have unity and integrity. This basic postulate underlies most religious traditions. In Islam, it is expressed by the doctrine of "tawhid," the absolute oneness of God. Tawhid shapes and colors everything Islamic from theology and science to art and language. As an article of faith, it seeks to present a unified and integrated vision of reality. But it is a mistake to treat unity only as a matter of theology. Unity is a framework of analysis and understanding, a context in which reality emerges as an interconnected whole. Taoist sages, Native American medicine men, Hindu gurus, Greek philosophers, Jewish, Christian and Muslim thinkers and mystics all have had a sense of the cosmos as an ordered whole. Our five senses perceive the world as a whole. I see, smell and hear things as integrated wholes. Conceptually, our minds conceive beings not as broken things but as interconnected units. What we call "reality" is intelligible and thus amenable to rational analysis only when it is conceived as a whole. The incredible variety and diversity we see in the world is not lost in my holistic perception of it.This is so because there is a difference between unity and uniformity. Uniformity denotes a state of bland sameness and oppressive homogeneity. Unity points to what connects diverse things. There is no uniformity in nature but unity reigns in the natural order. Uniformity is produced by man-made machines and devices. The unity of an animal species does not amount to uniformity. Each animal, while belonging to the same species, remains unique and maintains its particular personality. But the series of machines produced in exactly the same ways leads to monopolizing uniformity. Living beings have "identity," machines have "serial numbers." In the Islamic tradition, Ibn al-Arabi uses concept of "unity-in-diversity" (al-wahdah fi'l-kathrah) to explain the evasive relationship between unity and multiplicity. For him, unity does not negate plurality. Rather, it places plurality, multiplicity and diversity within a larger context of intelligibility. Plurality and diversity are essential traits of the world of creation. But diversity by itself does not give us the concept of the world. Otherwise, we would not be able to make sense of the sky, the earth, the seasons, human beings and their relations. It is through their unity-in-diversity that things maintain their essential identity and variety at the same time. Unlike uniformity, unity does not reduce a garden to a single flower. Unity-in-diversity recognizes the individual character of each being. But it also elevates them to a higher order of meaning whereby differences do not lead to chaos, incoherence, collision and ugliness. Just as we recognize the individual reality of each Ahmad, John, Arjun, Li and so on, we also acknowledge their essential humanity beyond ethnic, cultural and linguistic traditions. As Ibn Arabi suggests, we can have a relationship of complementarity between unity and diversity. But it requires a higher point of reference by which unity and diversity are each given their due. Recovering this principle can help us overcome many of the unnecessary ethnic and sectarian tensions we lament to see today.