How did John C. Eccles and Karl Popper defend forms of mind-matter dualism?

In the context of 20th-century philosophy, John C. Eccles and Karl Popper advocated for a form of mind-matter dualism that diverged from traditional Cartesian models. Rather than strictly adhering to a two-part division of reality, they proposed a tripartite framework that categorized existence into matter, mind, and ideas. This approach is often considered more Platonic than Cartesian in its structure.1

While Eccles, a neurophysiologist, developed theories regarding the mind as a nonmaterial entity, his collaboration with Popper focused on this three-tiered ontological system. By distinguishing between physical matter, the conscious mind, and the realm of ideas, they sought to address the complexities of human experience that materialist accounts often struggle to explain. Their work represents a notable attempt to defend a dualistic perspective during a period when physicalist and materialist theories of the mind were increasingly dominant in scientific and philosophical discourse.1