96 Herlert Spe7ice7'''s Synthetic Pliilosophy. 



sensations or conscious states. In some persons, vibrations 

 as different in velocity as those which commonly cause red- 

 ness and greenness awaken identical sensations. Luminous- 

 ness is a sensation produced by the action of waves of ether 

 upon the retina and fibers of the optic nerve. This sensa- 

 tion may also be produced by a blow or by electricity, which, 

 singularly enough, while it causes luminous phenomena 

 through the eye, brought in contact with other parts 

 gives rise to quite different sensations — sounds in the ear, 

 taste in the mouth, ticklings in the tactile nerves. That 

 tastes and odors are not intrinsic in things with which we 

 associate them is very evident. The sweetness of sugar 

 and the fragrance of the rose are sensations in us caused by 

 these objects, the one appreciated by the sense of taste, the 

 other by the sense of smell. Heat, too, is a sensation, and 

 is conceivable objectively only as a mode of motion. 



Another quality which we ascribe to things is hardness ; 

 but hardness can not be intelligently conceived except as a 

 feeling. When we say that a stone is hard we mean that, 

 if we press against it, we experience a sensation of touch, 

 a feeling of resistance, which is designated by the word 

 " hardness." To illustrate that both hardness and form be- 

 long to the groups of our conscious states which we call 

 sensations of sight and touch Huxley observes : " If the sur- 

 face of the cornea were cylindrical we should have a very 

 different notion of a round body from that which we possess 

 now ; and if the strength of the fabric and the force of the 

 muscles of the body were increased a hundredfold, our mar- 

 ble would seem to be as soft as a pellet of bread crumbs." 

 What we call impenetrability is the consciousness of exten- 

 sion and the consciousness of resistance constantly accom- 

 panying one another. What we call extension is a con- 

 sciousness of relation between two or more coexistent states 

 produced through the sense of sight or the sense of touch. 

 Even the conception of vibrations among particles of mat- 

 ter, mentioned above as objective factors in the i)roduction 

 of sound and color, is but an inference from states of con- 

 sciousness caused in us by vibrations which have been ap- 

 preciated by the optic or tactile nerves ; in other words, by 

 subjective experiences produced in us by some unknown 

 cause. 



Thus, what are popularly believed to be qualities and 

 states of matter — sound, color, odor, taste, hardness, exten- 

 sion, and motion — are names for different ways in which 



