 Shepherd recognizes two basic cognitive faculties: sense, or the ability to have sensations of all varieties, and understanding, or the ability to reason from the occurrence of sensations. Whenever the mind produces an idea, there is a sensation of it. Consciousness is the genus of sensations; sensations are just entities of the sort that appear in consciousness (EASP: 135). Its species include sensations of sensible qualities, sensations of ideas of memory, ideas of imagination, ideas of reason, and so on. Properly speaking, sensations of ideas are of nothing but an idea and the idea refers to, or represents, something considered to be different from the sensation. They are not sensations of the thing ideas purport to represent.  Sensations of the first sort, i.e. sensations of sensible qualities, are sensations caused by qualities such as motion and color with aid of the organs of sense.  We follow Shepherd in this use of ‘sensation’.  We also follow her in using ‘perception’ to mean the notice taken of sensations.  But ‘sense perception’ refers to cognition of external objects by means of the senses.  