The book is centered around one idea: Emergence. What is emergence? It is a physical principle of organization which explains how possibly complex phenomena arise from how different constituents are organized, not the properties of the parts within. Laughlin puts forward one thesis: most higher level physical laws are consequences of emergence--- arising from collective self-organization, rather than being sensitive to the details microscopic rules.
Although he makes no explanation for where such principles of organization may arise from, as would probably be impossible anyone to do without speculation, Laughlin provides illustrations from physical science to help the reader understand this concept. One such insightful illustration is the following: “Since principles of organizations --- or, more precisely, their consequences, can be laws, these can themselves organize into new laws, and these into still newer laws, and so on. The laws of electron motion begets the laws of thermodynamics and chemistry, which beget the laws of crystallization, which beget the laws of rigidity and plasticity, which beget the laws of engineering. The natural world is thus an interdependent hierarchy of descent.”
Laughlin goes further to make the non-trivial claim that there is no real distinction between "fundamental laws" and laws descending from them. "What physical science has to tell us is that the whole being more than the sum of its parts it not merely a concept but a physical phenomenon. Nature is regulated not only by a microscopic rule base but by powerful and general principles of organization." This may be quite counterintuitive since we may quite used to thinking of the basic unit as more fundamental and basic, and to the idea of reductionism being at the heart of scientific investigations (in many cases, at least).
To support his view, Laughlin provides physical examples about the ideal gas law, semiconductor physics, phase transitions, astronomy. He presents us with experiments to challenge our conception of the bottom-up approach being more “fundamental”. The most compelling among these are the measurements of “fundamental” constants such as the elementary charge. It turns out that the most accurate and precise value is not obtained by a sophisticated measurement setup with a huge apparatus measuring the charge of electrons stripped from atoms, but determined from the Josephson constant in the context of superconductivity, and the von Kiltzing constant from the Quantum Hall Effect. Both of these experiments involve very imperfect crystal samples, and a large number of atoms, and yet it is in these collective phenomena that we seem to find the most certainly in these fundamental values. Collective behavior seems to determine attributes of “individual particles”? Interestingly, the notion of the “wave property of matter” would make more sense when we view waves as some collective motion. Frankly, it is hard to wrap your brain around these, but this is a good argument for the case that the simplest and basic physical laws come not from the parts, but the whole. In Laughlin’s own words, “Exactness is a collective effect that comes into existence because of a principle of organization.”
Even if you are unfamiliar with higher-level physics and never heard of renormalization or knew much about ether, the properties of vacuum, or quantum theory, you can find some understanding of these and other ideas in the many non-science examples and analogies from daily life and society.
Overall, “A Different Universe” is witty and quite eloquently written, and an insightful and enjoyable read.