John starts off by reminding the audience of the levels of things we find in reality: quarks, chairs, mountains, galaxies, and beyond! But he and Ken note that this show’s sense of ‘levels’ is more about layers than it is about sizes. Is a nation of a million people a different layer of real than a million people living together? Is a mind a different layer of real than a bunch of particles in a cranium? Are numbers a different kind of real than symbolic markings on our pages? To answer these questions, Ken and John take the conceptual tools out of their philosophical toolbox, namely, the concepts of reductionism and emergence. The former says that the essence of a higher ‘level’ of reality (like a mind) can be genuinely explained in terms of lower levels (like molecules in a brain); the latter says that it cannot. 

In the next section of the show, Ken and John introduce their guest, Timothy O’Connor, and talk to him about emergence and reductionism as it pertains to human consciousness: does consciousness emerge as a new kind of (non-physical) property from the physical properties of our brain, even if the physical properties seem to determine what goes on in conscious mind? Can we understand what happens with physical realities as caused by what happens in a non-physical mind? As they explore these questions, they discuss dualism, free will, and the boundary between reconcilable and irreconcilable differences.

In the final section of the show, Ken, John, and Tim  discuss the implications of reductionism and emergence for religion and epistemology (the study of how we know things). Can emergence help us better understand religious ideas, like the existence of the soul and of immortality? Is  reductionism and emergence properties of the way the world actually works, or are they just concepts that are helpful for us to use in explanations: are disagreements about these fundamentally a metaphysical or a epistemological one? John finally resolves to answer these questions by reciting a poem.

• Roving Philosophical Report (Seek to 6:30): Julie Napolin interviews Stanford biology professor Deborah Gordon, who studies how order emerges from apparently uncoordinated behavior in ant colonies.

• 60-Second Philosopher (seek to 49:50): Ian Shoales explains the existence and significance of supervenience, an important conceptual tool for understanding emergence and reductionism.