You are a person, I am a person, but what is a person? (and why does it matter?) Fourteen-hundred years ago Boethius said 'person' is the 'individual substance of a rational nature / rationalis naturae individua substantia'. Boethius' Aristotelian conception of the person was then re-affirmed by St Thomas Aquinas in the high middle ages, and thereby carried through into the modern age as a necessary part of Latin Trinitarian theology. For us, 'person' still means 'an individual rational being'. But it also implies much more, such as the dignity and the relationality and --lately but most importantly -- the unicity, of such a creature. This lecture will ask how native are these scholastic and modern developments to the Boethian definition of 'person', and whether the Boethian definition is still fit for purpose.