This title presents an investigation of how understandings of theosis in the Christian Tradition have related to understandings of divine nature in terms of koinonia. Discussion of theosis is mainly undertaken within Byzantine Orthodoxy and is usually structured around an examination of patristic and medieval sources. This work builds upon such discussions and broadens the basis by including Western sources (Catholic and Protestant) in contemporary debates about salvation. In seeking to explore a relational understanding of divine nature, a discussion of personhood and communion is held. This is filtered through the works of Zizioulas, exponents of communion ecclesiology and those such as Turcescu who have provided a critique of these understandings. This is an investigation of how understandings of theosis in the Christian Tradition have related to understandings of divine nature in terms of koinonia. It further suggests a relational paradigm for conceptualising how theosis may be understood today, drawing out implications for the Christian community and discipleship.