The term ‘internal perception’ typically indicates the experience humans have of what happens inside their bodies, i.e., their bodily states and changes. In the literature, these were mostly considered as parts of two main body monitoring systems, known as the interoceptive and proprioceptive systems. This paper explores the concept of internal perception and suggests that for the purposes of philosophical research, it can be considered as the product of a unified propriosensitive system that provides a constant, dynamic mapping of internal states and their changes. The study examines some positions contending that bodily signals do not constitute a proper form of perception and argues that, on the contrary, proprioceptivity is entirely analogous to exteroception in all significant aspects. This involves identifying criteria to establish under what conditions something can be defined as a form of perception and whether internal perception meets these criteria. The underlying idea of this essay is that internal perception plays a fundamental role in understanding human cognition, although it has traditionally been neglected by philosophy and – more generally – by cognitive research which have predominantly focused on exteroception, and particularly on vision, as the privileged sensory modality for knowledge acquisition. Lastly, the paper calls for a more rigorous examination of the propriosensitive system, suggesting that internal perception represents a largely untapped field in philosophical inquiry, with potential to reshape our understanding of the epistemological role of the body in knowledge acquisition.
