Today sees the publication of “Laudato Si”, the Pope’s encyclical on the environment. Encyclicals are for Catholics (and there are 1.2 billion of them in the world) but in this one, Pope Francis aims to “address every person who inhabits this planet”. In it, he warns of the impacts of climate change and calls for changes in consumption and production patterns, as well as offering theological reflections on the relationship of humanity to the natural world.

A draft of the encyclical was leaked on Tuesday, and has given some commentators a chance to sneak in some early analysis – some delving into the theology of the text, others seeking to connect it to a more general and non-denominational spiritual connection with nature.

I think both readings have something to offer – and other responses are possible too: this is a political text (the Pope is a head of state and diplomat as well as a spiritual leader, and has previously commented on climate change agreements), and should be seen in the context of a long line of attempts to set the tone of debates on morality and ethics within the church, but also beyond it – with mixed results and reactions.

For me, though, this encyclical is significant and interesting in a number of ways. It articulates a contemporary Catholic position on the relationship of humanity to the rest of creation in the light of ecological challenges we face. That’s a position that is distinctive and different in very radical ways from any number of UN reports, mission statements, corporate responsibility plans, worldwide consultations and so on.

The Catholic – and, in particular, Franciscan – element of this is fundamental. “Laudato Si”, the encyclical’s title, is a reference to St Francis’ Canticle of the Creatures with its references to “Brother Sun”, “Sister Moon”, “Brother Wind”, “Sister Water”, “Brother Fire” and “Sister Mother Earth”. St Francis of Assisi wrote it in 1225, a year before his death.

This song is the key to the Pope’s encyclical. It positions us in a very particular relationship with our fellow humans, but also with other parts of creation – that of brotherhood/sisterhood – which in turn is set in relation to God. We may or may not be in the Anthropocene, but this isn’t an anthropocentric view of the universe. Any analysis of the letter and its reception by Catholics worldwide, from Brazil to the Philippines, that glosses over that fact is bound to be inadequate.

The Pope also links this understanding of nature to St. Francis’ life and mission. The Saint’s poverty and simplicity of life are “una rinuncia a fare della realtà un mero oggetto di uso e di dominio” (“a refusal to treat reality as a mere object to be used or dominated”) (p.11). This isn’t to romanticise poverty or seek to impose it upon people, but is a call for the privileged and wealthy to live more simply, not as an end in itself, but in response to this fraternal relationship with other creatures.

For those who can’t relate to these theological questions, there is plenty to chew on in the document – the draft I saw (pdf) ran to 192 pages – from positions on the ‘technocratic paradigm’, culture, science-religion relations, technology, intergenerational equity and the need for dialogue.

But it is worth reflecting on the strangeness of a world in which a 790-year-old religious song can frame, however indirectly, international negotiations on climate change and global justice. Whether this influence is a good or bad thing, and whether this latest encyclical’s meaning for a billion Catholics will lead to any traceable influence on what happens, is open to question, but “Laudato Si” will have a peculiar and unique place in the story of this crucial year for ongoing debates on sustainability and development.