Brain imaging technologies are increasingly used to find networks and brain regions that are specific to the functional realization of particular aspects of the self. In this paper, we aim to show how neuroscientific research and techniques could be used in the context of self-formation without treating them as representations of an inner realm. To do so, we show first how a Cartesian framework underlies the interpretation and usage of brain imaging technologies as functional evidence. To illustrate how material-technological inventions (...) and developments can have a significant and lasting impact on views of the self, we show how this framework was influenced by another technology: the camera obscura. Subsequently, we show that brain imaging technologies challenge the idea that privileged access to the self can be obtained merely through introspection, indicating a strong discontinuity between the Cartesian and the current neuroscientific framework. Building on these insights, we reframe the self in terms of self-formation. This view neither regards the brain as an independent realizer of aspects of the self, nor assumes that self-knowledge can be obtained through introspection. From this perspective, self-formation is realized throughcritical self-identification: instead of offering representational knowledge of an ‘inner self,’ the potential use of brain imaging technologies within this framework lies in their capacity to offer what we call ‘extrospective knowledge’ that pragmatically can contribute to self-formation. Brain imaging technologies contribute to this process because they foreground our neurophysiology, which helps to critically integrate biological aspects into self-formation. (shrink)