He "was a strong advocate and collaborator with his long-time friend, Sir Karl Popper, in promoting understanding of an approach to science, in which the scientist must formulate a hypothesis and deduce from that consequences that can be falsified by testing. "In his specialty of neuroscience, he was a forceful and nearly singular voice upholding the view that the human mind included a part existing distinctly from the physical brain and not explainable as an epiphenomena of that brain."
Eccles opposed scientific reductionism:
- I maintain that the human mystery is incredibly demeaned by scientific reductionism, with its claim in promissory materialism to account eventually for all of the spiritual world in terms of patterns of neuronal activity. This belief must be classed as a superstition. . . . we have to recognize that we are spiritual beings with souls existing in a spiritual world as well as material beings with bodies and brains existing in a material world. --Evolution of the Brain, Creation of the Self, p. 241 
In addition to this purely scientific study of the brain, Eccles has followed Sherrington in developing a philosophy of the human person that is consonant with the whole of brain science. Nobel Prize bio
Over the course of several decades, partly in collaboration with the philosopher of science Sir Karl Popper, Eccles has developed an alternative theory of the mind, known as dualist-interactionism. - David Pratt 
- http://nobelprize.org/nobel_prizes/medicine/laureates/1963/eccles-bio.html - Sir John Eccle's biography.