Roots hold me close
Every religious tradition needs roots. We need the forebears who shaped our traditions and our thinking. If we were not proud of them, why would we want to be part of our tradition? We need the spiritual practices, rituals and symbolism of our tradition - these are the things that transform us, and help us to cohere as a community.
How does ritual effect transformation? By allowing us to symbolically represent the inner processes of our individual and collective psyche, and change their relationships to each other.
What are the rituals of Unitarianism? There's the hymn sandwich (yes, it is a ritual), the Flower Communion, the Water Communion, the lighting of the flaming chalice. There's communion. We need these rituals because they are part of our identity as a worshipping community.
But we also need personal spiritual practice, which we have the freedom to choose from many different traditions. However, our roots lie in the Christian tradition, and if we chop off our roots, the plant might die. We can learn about lectio divina, prayer beads, contemplative prayer, and liberal and mystical Christian theology. All of these practices and traditions were developed by people who were rooted in the same culture that we are, and they fit in with our cultural background. We also have roots - albeit further back - in the pre-Christian polytheist traditions of these islands, and these inform many of our folk customs and festivals.
Of course there's nothing to stop us from learning the spiritual traditions and practices of others, but let's be careful to avoid a shallow engagement with them, one that is not rooted in the philosophical outlook of the tradition being borrowed from. It's worth reading this critique of Pagan UU rituals, which points out that they are often engaging with the fluffy end of Paganism, rather than the full depth of Pagan theology. I have 20 years' experience of Pagan rituals, and they have considerable transformative effect and powerful resonance. I also practice Buddhist meditation (specifically Metta Bhavana), which I find really helpful.
Wings set me free
So I am not by any means arguing that Unitarianism and UUism should only use Christian practices - it could be argued (by those who do not view us as Christian) that this is also a form of cultural appropriation, depending on whether you see Unitarianism as post-Christian, universalist, interfaith, multi-faith, or something else. What I am suggesting is that we should feel free to explore Christian mysticism alongside other spiritualities, and that whatever tradition we are drawn to, a pick and mix approach, or a shallow engagement with it, will most likely not be conducive to spiritual growth.
I think we need to be aware of what we are doing when we borrow any practice, whether it is Pagan, Christian, Buddhist, or whatever. What is the underlying theology and philosophy of the practice? Is it compatible with our values, theology and philosophy? If we adapt the practice to fit our values, theology and philosophy, have we taken the soul out of the practice and made it into something else? If this is the case, should we rename the practice? If we are going to engage with Buddhist or Jewish or Pagan practices, we need to do so in a mindful way, with an understanding of the underlying philosophical tenets of Buddhism, Judaism or Paganism.
Given the way that the Christian ritual of communion has developed, is it valid for Unitarian communities to practice bread-and-wine communion? (I'd say yes, because we have always done so with our own interpretation of what it means, which is not so far away from other liberal Protestant groups.)
Unitarianism has also developed its own special rituals and symbolism, which help us to form our identity. These are our wings, if you like. Many religious traditions have their own special rituals and prayers and symbolism that make them unique (the Druids have the Awen and the Druid's prayer; Wiccans have cakes and wine; Quakers have Meeting for Worship; Anglicans have their liturgical traditions; and so on). Different Christian denominations do communion differently, and with a slightly different underlying theology.
We can interpret rituals and symbolism differently from others, but we should be aware of their history and origins, and not lift them out of context without considering the theological and philosophical implications.
Unitarians and UUs cherish our freedom, but let's not use it for a shallow engagement with spiritual practices. Let's use it to engage meaningfully with theology and symbolism and ritual, and to enrich our understanding of both our own tradition and others. If you are not rooted in your own tradition, it's difficult to engage meaningfully with other traditions.
Religions are like languages - you can speak more than one language, but if you don't know the grammar of your own language, it's difficult to learn another one.
I've practised Wicca for 20 years, so I would say that I speak the language of Wicca really well. But I was brought up as a Christian, so I speak that language too. Whether I like it or not, Christianity informs my thinking to a certain extent (even if I am reacting against some aspect of it). Over the last three years, I have immersed myself in Unitarian history and thought, so I would say I speak that language pretty well too. I also see it as a distinct language, rather than as a dialect of Christianity.
One of the things that I really value about Unitarianism is that it allows me to speak in all three languages, and to offer translations between them - as well as bringing in concepts from other religions which may shed some light on the ideas being discussed.
I also find it helpful to interpret and critically evaluate ideas from all three traditions in the light of ideas from other religions. The ideas of Sufism (which was partly derived from Neoplatonism and Gnosticism) are particularly helpful for understanding what Jesus was talking about. The ideas of Hinduism are really helpful for developing a deeper engagement with Pagan theology and philosophy.