Comprehensive AI Services (CAIS) is an approach to understanding proposed by K. Eric Drexler. In Drexler's words, «CAIS provides a model of flexible, general intelligence in which agents are a class of service-providing products, rather than a natural or necessary engine of progress in themselves.» (Drexler 2019: g1) On this approach, advanced AI systems are conceived as "services", or systems with an expanding set of capabilities, one of which is the optional capability of agency.