Recently, the usage of plagiarism detection software such as Turnitin® has increased dramatically among university instructors. At the same time, academic criticism of this software's employment has also increased. We interviewed 23 faculty members from various departments at a medium-sized, public university in the southeastern US to determine their perspectives on Turnitin® and student plagiarism. We wanted to discern if there are important disciplinary differences in how instructors define and handle plagiarism; how instructors use Turnitin®; and if instructors' thinking aligns with ethical and political concerns commonly expressed in the academic literature. Despite varying attitudes towards Turnitin®, those interviewed did not differ significantly in their views as to what student plagiarism is or its seriousness, and typical objections to "policing" plagiarism and Turnitin® had little resonance with interviewees. The majority viewed a substantial amount of plagiarism they encountered as unintentional and penalised only what they considered to be extreme versions of intentional plagiarism. However, often this contradicted the way they presented the concept of plagiarism in their syllabi and their classrooms. Surprisingly, these patterns were consistent among those who employed the software frequently and those who did not.