In everyday life, we take ourselves to be agents who could have decided and, hence, acted differently from how they actually did. However, in contemporary metaphysics, free will in this robust sense is controversial as it does not appear to fit into the natural world. In this lecture I show that the metaphysicians’ long-standing difficulties with free will originate from their difficulties with explaining how agency as such fits into the natural world. I argue that a fundamental revision of metaphysical assumptions is required. Metaphysicians ought to give up the common mechanistic-physicalist view of nature, and the traditional ontology of static things that sustains it, in favour of a metaphysical framework that recognises the biological and, hence, processual constitution of agents. The bio-processual account of agency that I suggest paves the way for a novel, scientifically informed defence of free will.