Henry Stapp did his doctorial work under the direction of Nobel Laureates Emilio Segre and Owen Chamberlain. He created the theoretical framework for the analysis of the scattering of polarized protons, and then analyzed the data obtained from the experiments at the Lawrence Radiation Laboratory at the University California in Berkeley, obtaining the phase shifts first at 360 Mev at later at higher energies. His work was the first large-scale computer analysis in high-energy physics.
Subsequently he worked closely with Wolfgang Pauli in Zurich on parity violations, and on fundamental problems in quantum theory. He wrote there an essay entitled “Mind, Matter, and Quantum Mechanics,” which developed into a book of the same title published 35 years later. He has written over 300 technical and mathematical published papers pertinent to basic foundational issues. During the sixties he was a principal mathematical and philosophical spearhead of new approach to quantum theory known as S-Matrix theory. He worked in Munich with Heisenberg on the problem of the interpretation of quantum theory, and later in Austin with
Wheeler on the same subject. His paper “The Copenhagen Interpretation” is widely recognized as a seminal work on this subject.
In 1968 he wrote his first paper about the apparent need in quantum theory for faster-than-light transfer of information. This issue had been raised in the paper about the Einstein-Podolsky-Rosen "paradox" published in 1964 by John Bell. Stapp has been, ever since, a principal protagonist in the continuing developments pertaining to this fundamental issue. His most recent works focus on the strong influence of quantum processes on the working of the brain, and specifically on the fact that quantum theory brings conscious choices by human agents irremovably into the physical theory in a way that directly accounts for the ability of a person's conscious choices to causally influence the activity in his or her physical brain.