1. What is a sensation?
External objects give an impression to the senses and are perceived by a reason, that is, to obtain an idea or some experience of them.
By our five senses we can acquire a “sensitive” knowledge of what is material and specific. By our reason we obtain an “intellectual” knowledge, which is abstract and spiritual.
Sensitive knowledge (from an inferior order) is sensation, perception and image. Intellectual knowledge (from a higher order) is concept, judgment and reason.
A sensation is a conscious impression of a material object in the sense organs: sight, hearing, taste, smell and touch.
Elements that take part in sensations are three: physical, physiological and psychical.
When we hear a song, physical factor is the vibrating air, physiological factor is the operations in the eardrum, the middle ear ossicles, the labyrinth and the auditory nerve, which sends the impression to the brain, and psychic factor is to ear a song and know that it like us.
Physical factor is outside us, physiological one is in our body and psychic one is in our soul.