This article describes how biology textbooks can work to discursively constitute a particular kind of "ethical subjectivity." Not only do textbooks constrain the possibilities for thought and action regarding ethical issues, they also require a certain kind of "subject" to partake in ethical exercises and questions. This study looks at how ethical questions/exercises found in four Ontario textbooks require students and teachers to think and act along specific lines. These include making ethical decisions within a legal-juridical frame; deciding what kinds of research should be publically funded; optimizing personal and population health; and regulation through policy and legislation. While engaging ethical issues in these ways is useful, educators should also question the kinds of (ethical) subjectivities that are partially constituted by discourses of science education. If science education is going to address twenty-first century problems such as climate change and social inequality, educators need to address how the possibilities for ethical engagement afforded to students work to constitute specific kinds of "ethical actors."