The student usually experiences great difficulty in distinguishing between _sensation_ and _perception_. A sensation is a simple report of the senses, which is received in consciousness. Perception is the _thought_ arising from the _feeling_ of the sensation. Perception usually combines several sensations into one thought or percept. By sensation the mind _feels_; by perception it _knows_ that it feels, and recognizes the object causing the sensation. Sensation merely brings a report from outside objects, while perception identifies the report with the object which caused it. Perception _interprets_ the reports of sensation. Sensation reports a flash of light from above; perception interprets the light as starlight, or moonlight, or sunlight, or as the flash of a meteor. Sensation reports a sharp, pricking, painful contact; perception interprets it as the prick of a pin. Sensation reports a red spot on a green background; perception interprets it as a berry on a bush. Moreover, while we may perceive a simple single sensation, our perceptions are usually of a group of sensations. Perception is usually employed in grouping sensations and identifying them with the object or objects causing them. In its identification it draws upon whatever memory of past experiences the mind may possess. Memory, imagination, feeling, and thought are called into play, to some extent, in every clear perception. The infant has but feeble perception, but as it gains experience it begins to manifest perceptions and form percepts. Sensations resemble the letters of the alphabet, and perception the forming of words and sentences from the letters. Thus _c_, _a_, and _t_ symbolize sensations, while the word "cat," formed from them, symbolizes the perception of the object. It is held that all knowledge begins with sensation; that the mental history of the race or individual begins with its first sensation. But, while this is admitted, it must be remembered that sensation simply provides the simple, elementary, raw material of thought. The first process of _actual thought_, or knowledge, begins with perception. From our percepts all of our higher concepts and ideas are formed. Perception depends upon association of the sensation with other sensations previously experienced; it is based upon experience. The greater the experience, the greater is the possibility of perception, all else being equal. When perception begins, the mind loses sight of the sensation in itself, for it identifies it as a quality of the thing producing it. The sensation of light is thought of as a quality of the star; the pricking sensation is thought of as a quality of the pin or chestnut bur; the sensation of odor is thought of as a quality of the rose. In the case of the rose, the several sensations of sight, touch, and smell, in their impression of the qualities of color, shape, softness, and perfume, are grouped together in the percept of the complete object of the flower.