ABSTRACT
That relation between object and subject which is established in the act of perception, is of a threefold kind. It assumes three distinct aspects, according as there is some species of activity on the part of the object; on the part of the subject; or on the part of both. If, while the subject is passive, the object is working an effect upon it—as by radiating heat, giving off odour, or propagating sound—there results in the subject, a perception of what is usually termed a secondary property of body; but what may be better termed a dynamical property. If the subject is directly acting upon the object by grasping, thrusting, pulling, or any other mechanical process ; and the object is reacting, as it must, to an equivalent extent; the subject perceives those variously modified kinds of resistance which have been classed as the secundo-primary properties; but which is preferred to class as statico-dynamical.
