This chapter introduces Integrated Assessment Models (IAMs) and explains how the models increasingly engage with feasibility. Beginning with a brief history of IAMs, the chapter distinguishes between two primary classes of IAMs: Cost-Benefit IAMs (CB-IAMs) and Process-Based IAMs (PB-IAMs). While CB-IAMs focus on optimizing the balance between mitigation costs and climate impacts and have been extensively debated in philosophical circles, PB-IAMs remain relatively underexplored in climate philosophy and ethics despite their centrality to the science-policy interface. PB-IAMs differ from CB-IAMs by taking predefined climate goals – such as temperature targets – as fixed inputs and modeling the “mitigation pathways” required to achieve them. The chapter outlines the value PB-IAMs provide in understanding the complex interactions and dynamics at the heart of climate change mitigation. The chapter goes on to explain how IAMs use scenarios to explore possible futures and traces the recent evolution of PB-IAMs, particularly their increasing application in assessing the feasibility of climate goals and pathways. It is this recent history of assessing feasibility that should be of particular interest to climate philosophy.