"In the nineteenth century psychology emerged as the interface between philosophy and the natural sciences. It addressed the eternal questions of philosophy by deed rather than by word: it embraced scientific methods to frame the questions empirically."  
 
Nicholas Wade, Psychologists in Word and Image, xiii - xiv.  
 
 
"Koch ...., in his influential history of the development of psychoogy, observed that psychology settled on its way of answering questions -- its methods -- before it developed its questions. The natural sciences developed their methods as a specific response to particular theoretical problems: Problems and questions came first, and method came second.... Psychology, however, was born of a determination to apply the methods of positivistic science to human beings. Only those questions that could be cast in ways amenable to scientific study were taken up by the discipline."  
 
Brent Slife and Richard Williams, "Toward a theoretical psychology", American Psychologist, 52(2), 117 - 129.  
 
 
"Since it got truly launched as a discipline and a profession in the last half of the nineteenth century ... the self-proclaimed 'science of the mind' has not just been troubled with a proliferation of theories, methods, arguments, and techniques. That was only to be expected. It has also been driven in wildly different directions by wildly different notions as to what it is, as we say, 'about' -- what sort of knowledge, of what sort of reality, to what sort of end it is supposed to produce. From the outside, at least, it does not look like a single field, divided into schools and specialties in the usual way. It looks like an assortment of disparate and disconnected inquiries classed together because they all make reference in some way or other to something or other called 'mental functioning'. Dozens of characters in search of a play...."  
 
Clifford Geertz, Available light: Anthropological reflections on philosophical topics, pp. 187 - 188.  
 
 
"No science is more intimately and practically related to the conduct of human life than is psychology. It is, indeed, concerned primarily with those facts and principles of experience and action upon which our understanding of ourselves as conscious beings and our ability to understand and sympathize with our fellows depend."  
 
Carl Seashore (1923), "Psychology as a Career", Science, LV, p. 381.