If Nature and Grace are opposed, eventually a dualism results which opposes God and the world, which distances God's activity from all natural processes (like mating insects...see below), which are then reified rather than seen as sustained by God, without occassionalism. For the Church, there can no such thing as pure, mere, autonomous nature since nature itself is the free creation of God, and therefore has freedom and love as its very substance, deeper even than - or perhaps somehow equivalent with - what we call 'matter.' (For more on the insidiousness of a concept of 'pure nature', see Conor Cunningham's amazing article, here.)
Yet creation must, in patristic fashion, be held as distinct from God, Who is the Uncreated; pantheism is avoided, divine and human freedom preserved, and yet the Incarnation affirms that God is closer to us than we are to ourselves, for the human nature has been taken up and transformed by the divine nature, and humanity - in the risen Christ - somehow participates in the life of the Trinity.
In light of all this, Bulgakov creatively extends the Orthodox position by describing creation itself as an act of grace. Valliere explains this well:
"The key to the Orthodox position [on the question of nature and grace] is the concept of ‘natural grace.’ The idea is that all creation, by virtue of its being and beauty, reflects the divine ground from which it springs:
'The beauty of the world is the effect of the Holy Spirit, of the Spirit of Beauty, and Beauty is Joy, the joy of being: 'Joy eternal nourishes / The soul of God’s creation.' This effect of the natural grace of creation, this breadth of the Holy Spirit in creation, the continuing, ongoing ‘brooding’ of the Holy Spirit over the ‘waters’ of creation, is the positive power of being.' (Bulgakov)
All cosmic activity, from angelic contemplation to the mating of insects, conforms with divinity “in as much as creation bears within itself the living image of the creator and stands in a relationship with him.” This ontological relationship is a divine gift, the original endowment bestowed on creatures by their creator as the “precondition for [their] sanctification through reception of the Holy Spirit.”
Indeed, Original grace is the foundation for all subsequent works of sanctification, including the outpouring of the Holy Spirit upon the church. […] The blessing of material things so exuberantly practiced in Orthodoxy – blessing of water, oil, bread, wine, crops, buildings, viands, and so on – [is an example of this] … The challenge is to forge creative linkages between the original grace which sanctifies all creation and the Pentecostal or ecclesial gifts revealed to the historic church” (Valliere Modern Russian Theology 352, 354).
One such creative linkage is inherent here, for Bulgakov (and Valliere) stress that the 'stuff' of creation is intrinsic to our priestly role in offering all of creation - freely given by God to us - back in praise and worship to him. In other words, to incorporate wine, bread, oil and water in the grace-bearing sacraments of worship is reciprocal to our use of them in our daily lives, as sustenance for our bodies which comes naturally from the earth. May we cultivate them to the health of both our souls and bodies, naturally, which is to say, grace-fully.