Chapter 2 of The Atheist’s Guide to Reality is probably the key chapter in the book. That’s where Professor Rosenberg lays out his view of physics and the nature of reality. He doesn’t mince words:
Everything in the universe is made up of the stuff that physics tells us fills up space, including the spaces that we fill up. And physics can tell us how everything in the universe works, in principle and in practice, better than anything else. Physics catalogs all the basic kinds of things that there are and all the things that can happen to them (21).
According to Rosenberg, “we should embrace physics as the whole truth about reality”. Why? Because science is a cumulative process, in which findings are confirmed, corrected or refuted, resulting in a solid foundation. Physicists are still learning things, but the “part of [physics] that explains almost everything in the universe – including us – is finished, and much of it has been finished for a century or more” (21).
Physicists, in particular, have discovered that everything in the universe is composed of either fermions (such as quarks, electrons and neutrinos) and bosons (like photons and gluons), and combinations thereof (like protons and molecules). Fermions are usually associated with matter, while bosons are usually associated with fields and forces. Rosenberg says that’s all there is:
All the processes in the universe, from atomic to bodily to mental, are purely physical processes involving fermions and bosons interacting with one another…Physical theory explains and predicts almost everything to inconceivably precise values over the entire body of data available…From a small number of laws, physics can neatly explain the whole trajectory of the universe and everything in it…The phenomenal accuracy of its prediction, the unimaginable power of its technological application, and the breathtaking extent and detail of its explanations are powerful reasons to believe that physics is the whole truth about reality (21-25).
But what about the other sciences? Surely, chemistry and biology, for example, say something true about reality. Rosenberg, however, argues that physics explains chemistry and chemistry explains biology. Everything that happens in your body is a chemical process, and every chemical process is a physical process:
The only causes in the universe are physical, and everything in the universe that has a cause has a physical cause. In fact, we can go further and confidently assert that the physical facts fix all the facts … including the chemical, biological, psychological, social, economic, political and other human facts (25-26).
He left out the geological and cosmological, but you get the idea. Higher-level sciences are in principle reducible to lower-level sciences. Philosophers call this view “reductionism”. Rosenberg is clearly a “reductionist” of some sort. A similar claim is that all higher-level facts depend or “supervene” on lower-level facts (this principle is called “supervenience”). Rosenberg asks us to imagine two regions of space-time, our own plus another millions of light-years away, in which every fermion and boson is arranged exactly the same way. In such a case, everything else in the two regions would be the same too. Regardless of the regions’ respective histories, if all the sub-atomic particles are arranged the same way, the two regions will contain the same rocks, the same birds and bees, the same political institutions, the same music, the same people with the same memories and thoughts. Physics fixes all the facts.
Next time, before continuing with chapter 2, we’ll consider whether it’s reasonable to “embrace physics as the whole truth about reality”.