Page:Mind-a quarterly review of psychology and philosophy, vol33, no130 (1924).djvu/12

 in a given moment is the sum of its relations to the remaining parts of this moment and is given once for all. Matter also cannot be defined in momentary space. Only when we compare the ordering of two different moments by means of permanent space can we see that a group of elements of experience, which are distinguishable by the same characters, coincides in both moments with a certain group of points of the permanent space of these moments, while another group of elements, which coincided in the first moment with a group of timeless points A, coincides in the second moment with another group of timeless points B. That we express by saying that one particle, on which we fastened our attention, remained at rest and a second moved from position A to position B in the enduring space which we are using for our comparison. Motion is thus change of position in permanent space, and rest is absence of motion.

Matter.—40. A definition of motion is incomplete without a definition of the subject of motion, which is matter (in the broadest sense of the term); we will, therefore, briefly indicate here how a definition of matter can be arrived at.

Of a group of attributes, which can be identified in all the elements of any progressive continuous figure of elements of experience, we say that it persists or endures, and call it a permanent group of attributes.

As we have already indicated above the mind is disposed, or compelled, to seek or form such enduring, unchanging characteristics of experience. If we call the progressive one-dimensional figure of elements of experience, which carries an enduring group of attributes, a perceptual particle—we can define a material particle as a perceptual particle composed of impenetrable elements of experience, where impenetrable elements of experience signify those elements of experience which cannot form a common ingredient of two different material particles.

41. In the definition of space and time we have achieved the aim which we set up at the beginning of this essay, and