<p>In scientific discourse, inquiry-based learning in science education is ascribed numerous potentials. However, despite scientific evidence of positive effects on the motivation and interest of learners, as well as on the critical thinking skills or academic performance of students and numerous published teaching concepts and materials, inquiry-based learning has not yet found its way into mainstream teaching. A&#xa0;similar discrepancy between academic discourse and teaching practice can be seen in dealing with uncertainty. While uncertainty is described theoretically as a&#xa0;central and inherent element of inquiry-based learning in sciences, it is often not addressed or even avoided in the classroom. With the aim of approaching the underlying mechanisms of this discrepancy, the study uses semi-structured interviews (<i>n</i> = 12) to investigate how practicing science teachers deal with the requirements of inquiry-based learning and the associated uncertainties. The grounded theory developed shows that teachers of science subjects experience an irresolvable tension between the norm of openness and goal orientation when implementing inquiry-based learning. On the one hand, this results from the permanent juxtaposition of inquiry-based learning and so-called normal teaching. On the other hand, it became clear that, from the perspective of teachers, tensions are inherent in the concept of inquiry-based learning itself. In many cases, the teachers strategies temporarily resolve the tension between openness and goal orientation by focusing only on one of the two poles. All strategies can be conceptualized as a&#xa0;change (I)&#xa0;in the thing itself, i.e., inquiry-based learning, (II)&#xa0;in others, i.e., the students or the school system, or (III)&#xa0;in oneself.</p>