The aim of this research is to analyse moral arguments of students in respect to meat consumption and livestock farming. In order to encourage discussion and reflection processes about morality and socio-scientific issues in biology classes, we explored the structure of moral conceptions based on a theory of mind. It is already claimed that human thinking is based on experience, and moral conceptions are also embodied and structured by metaphors (Lakoff & Johnson, 1999). Based on this theory, this paper will develop and give a perception of the Educational Moral Metaphors System as an instrument to identify and analyse moral conceptions. Upon this theory, we have developed and evaluated an evidence-based instrument to explore moral conceptions. The findings result from 5 teaching experiments with 15 students (10-16 years old). Therefore, in this article specific students’ conceptions and metaphors are examined on the basis of moral arguments and judgements by means of Qualitative Content Analyses. The results illustrate the Educational Moral Metaphors System as an analytical tool and how different moral arguments and students’ conceptions can be, as well as which recurring metaphorical structures can be found. In this paper we will illustrate that moral thinking is expressed in language by metaphors.