A physics-based understanding of how our conscious thoughts can affect our physically described brains is described. This understanding depends on the shift from the mechanical conception of nature that prevailed in science from the time of Isaac Newton until the dawn of the twentieth century to the psychophysical conception that emerged from the findings of Planck, Bohr, and Heisenberg.. This shift converted the role of our conscious thoughts from that of passive observers of a causally closed physically described universe to (...) that of active participant in an essentially psychophysical understanding of nature. (shrink)