In order to advance our understanding about the roles studentsassign to expert knowledge, the present study addresses how secondaryschool students use their knowledge of scientific disciplines in theirreasoning of socioscientific issues (SSI). Through group discussions, theresults show that students use science either as a sole justification orintegrated with other kinds of knowledge. Using expert knowledge to liftproblems out of the limited local contexts and find solutions, thestudents access the freedom to make personal choices. Thus, it wasconcluded that scientific knowledge provides possibilities for decisionsthat can support students' agency.