Abstract
The subject of mental processes or mental states is usually assumed to be an individual,
and hence the boundaries of mental features – in a strict or metaphorical
sense – are naturally regarded as reaching no further than the boundaries of the
individual. This chapter addresses various philosophical developments in the 20th
and 21st century that questioned this natural assumption. I will frame this discussion
by fi rst presenting a historically infl uential commitment to the individualistic
nature of the mental in Descartes’ theory. I identify various elements in the Cartesian
conception of the mind that were subsequently criticized and rejected by various
externalist theories, advocates of the extended mind hypothesis and defenders
of embodied cognition. Then I will indicate the main trends in these critiques.