Maxwell's demon has taught us that agents may have different descriptions of the same physical system, and thereby extract different amounts of work. In this talk we will explore the role of subjectivity in thermodynamics, both in classical and quantum settings.

We will start with the example of Landauer's principle, used to relate information and thermodynamic work, and extend it to the case where agents may have quantum information about the state of a system. We will also see how information can be transformed into different types of work depending on agents' restrictions and resources.

We will then lay out the idea of temperature as an operational concept, and how the same system may be act as a bath of different temperatures for different observers - depending on factors like correlations between agent and bath, the agent's instruments and their acceleration.