Abstract “The question of finding a merciful God. Understanding Martin Luther’s relation to metaphysics and ontology” Myrén, Anna. 2017, Master’s Thesis, 30 credits. E-mail: annamyren@live.se The Department of Theology, Uppsala University, Engelska Parken, Thunbergsv. 3B, Box 511, SE-751 20 UPPSALA, Sweden, info@teol.uu.se  This thesis examines arguments and premises for understanding Luther’s relationship to metaphysics and ontology. The main theoretical sources are firstly research that, on the one hand argue that Luther’s doctrine of justification has ontological structures and on the other treat his relation to metaphysics, and secondly sources that treat Luther’s development of theological themes and issues from a history of ideas perspective.  The thesis concludes that the arguments of Finnish Luther scholars Tuomo Mannermaa and Sammeli Juntunen are helpful for understanding the relationship between Luther, metaphysics and ontology. Their conclusions display different levels of structures in his doctrine; thematic as well as re-oriented structures of thought, showing that Luther is occupied with metaphysical and ontology and presenting strong arguments for his doctrine of justification as ontological. Luther’s doctrinal development can be understood both as a result of criticism of substance-metaphysics, as well as itself ultimately displaying metaphysical and ontological issues. Such contents in his theology should be viewed in the larger perspective of forming theology, a history of ideas context that broadens the question to one of structures of thought, involving themes, issues, forming of doctrine as processual development. However, their thematic, doctrinal focus risks not giving full account for understanding Luther’s relation to metaphysical and ontological issues. An intricacy of the question is displayed and possible to trace when Luther’s theology is addressed from systematical as well as historical perspectives. The thesis finally argues with the help of a history of ideas perspective that the theologia crucis - specifically with its concept of the hidden God, the deus absconditus – is a resource for further inquiry of Luther and metaphysics, in understanding his theology as describing reality.  Keywords: Luther, metaphysics, ontology, doctrine of justification, Mannermaa, Juntunen, themes, structures of thought, theologia crucis, deus absconditus.