Theorising and research in the field of environmental psychology has been dominated by two different schools of thought. The cognitive approach emphasises the primacy of cognitive processes on preference judgements between various types of environments and on the restorative effect of nature on humans. The competing psycho-evolutionary approach emphasises the primacy of affect. This theoretical fragmentation has contributed to environmental psychology's conceptual isolation in respect to its potential significance for other psychological sub-disciplines. This thesis proposes a new theoretical account, the "Resonance-Dissonance" (RD) framework of environmental perception, which provides a unifying framework for hitherto competing approaches in environmental psychology. It also seeks to contribute towards building and strengthening the tenuous or missing conceptual links between environmental psychology and other psychological sub-fields. A series of interlocking concepts, which bind together aspects of the relationship between perceivers and their immediate physical surroundings, is proposed to achieve this theoretical integration. Innate and culturally shaped needs and wants, in the form of mental structures providing reference patterns, are conceptualised as a fundamental aspect of the relationship between individual and environment. If the environment is appraised as having the agency to meet these needs, a state of resonance in the form of positive affect and cognitions ensues. Conversely, if the environment is appraised as not having this agency, a state of dissonance in the form of negative affect and cognitions emerges. These perceptually based cognitive-affective states are conceptualised to influence cognitions, emotions, behaviour, and physiology of the individual. Preference judgements and psycho-physiological restorative effects, as the main areas of theorising and research in environmental psychology, will be addressed. Possible theoretical implications, as well as practical applications, of the proposed RD framework on other psychological sub-fields are outlined and a tentative research programme is suggested.