This paper aims at reflecting on both subjectivity and the different devices that presently constitute it, such as Public Policies, by considering the articulation between truth, politics and ethics. This reflection follows the path of problematizations posed by Foucault and Agamben about the relationship between subjectivity and ethics, as well as about potency and life extermination. A letter written by Guarani-Kaiowás Indians from Mato Grosso do Sul/Brazil and published in 2012 is the thread that has conducted this discussion. The analysis has enabled us to consider that the approximation to discussions about ethics and politics, as well as the refusal of normative ways of living with the concept of potency and testimony, help us understand what Public Policies have produced as subjectivity and at the same time the non-exhaustion of life potency by the very exercise of Politics.
subjectivity; ethics; politics; potency of life