One may wonder what the term 'door' means. A door is the means through which citta experiences an object. Seeing experiences visible object through the eye-door. The eye-door is the eyesense, a phenomenon (rupa), which is capable of receiving visible object. Eyesense itself does not see but it is a condition for seeing. There are six doors of eyes, ears, nose, tongue, bodysense and mind- door. There is no self who experiences objects. There are only different types of cittas, succeeding one another, which experience an object through one of the six doors.