From this perspective and that of Genesis, the opposite of looking at, listening to, or grasping is not blackness, silence, or lack of pressure, but unstructured energy, energy that does not afford the perceiving of things or events in the world. The energy in the physical world and the energy coded by the receptors at the periphery are neutral. Perceiving is not merely attending to parts of the incoming energy, but is the abstraction of the structured energy out of the ongoing flux. It is the interpretation of the physical properties of objects and events. Hoffman (1998) described vision as an intelligent process of active construction: the world is not recovered or reconstructed. The act of looking or listening constructs objects. This is as true for seeing a tree in a snowstorm as it is for hearing a word in a thunderstorm. Perceiving is creative and not passive. The purpose of this book is to match up auditory and visual perception. Throughout, I take the position that perception is active and that we attend to the structured parts of the world. Therefore, I do not think of perception as a noun, but as a gerund, perceiving. Looking, listening, searching, overhearing, grasping, touching, manipulating, and so on are the processes of perceiving. These processes are multifaceted. There is no doubt that biological processes exist that transform and code the firings from the peripheral receptors. But, there is no general agreement about how those firings construct the world. On the one hand, the sensory data, if taken over time and space, may have sufficient information to create unambiguous percepts (Gibson, 1966). On the other hand, sensory data may be inherently ambiguous, so that there are necessary inferential and heuristic processes to make sense of every firing pattern. The best strategy would be to make use of cues that are most likely to be correct and have the least variability (Jacobs, 2002). Following Helmholtz (1867), we would perceive what in the past would have most likely generated the sensory data (Purves, Lotto, & Nundy, 2002). It is not necessary or even appropriate to claim a predominant role for any level of processing. Rather, we make use of all levels to create the appearance of things. All Sensations Belong to Things and Are Understood With Respect to Those Things As a first guess, visual stimulation is assumed to come from one or more reflecting surfaces of rigid objects moving in three dimensions, and auditory stimulation is assumed to come from one or more continuously vibrating 4 Perceptual Coherence