'Being in Christ' is a central theme in the message of the gospel. It is central for understanding the relation of Christian believers and the church with Jesus Christ, their Lord. It determines the identity of a Christian. It is helpful for understanding the presence of Christ and his salvation in the present. It can be developed as an element of a theological ontology. Finally, it is a theme with a great integrating power. In this book, the theme 'being in Christ' is analyzed in different perspectives. The attention is focused on the reality of 'being in Christ': its ontological implications. First, two representatives of the Reformed tradition are investigated: the English Puritan John Owen and the Dutch Neo-Calvinist Herman Bavinck. Second, a reconstruction of the Pauline and Johannine perspectives on 'being in Christ' is provided. Third, the theme is examined in the work of the English ethicist Oliver O'Donovan and the German-Swiss theologian Ingolf U. Dalferth. In the final chapter, the author gives his own systematic-theological proposal of a concept of 'being in Christ.'