Thorn within: the environment in personal identity

“We have never been individuals.” This shady statement obscures the complexity of defining biological individuals. Some authors, departing from ecological developmental biology, have argued that humans are holobionts, an assemblage of organisms comprising a host and symbionts. It has then been taken to imply that human beings are not individuals. However, it seems complicated not to take the individual as a reference point. Humans consider themselves physically bounded entities with agency and self-determination. While I contend that integrating biological facts in discussions about individuality is essential, I do not discard the notion of the individual altogether, as some authors have suggested. In this paper, I propose that starting from the idea of personal identity can be a fruitful approach to reconsidering the notion of an individual while accounting for these biological facts. I argue that a human being’s sense of individuality is rooted in personal identity, for which the brain is the necessary condition. Since neuroepigenetic mechanisms significantly shape the brain, personal identity is shaped by the environment, which opens a path to a notion of an individual that integrates biological findings.