LEVELS OF REALITY

John Perry

If you think about it, reality comes in many levels, each level involving different kinds of things, having different kinds of properties. Perhaps most people would think of things like dirt at the bottom level, then us at the next level, and the sky at the highest level. But philosophers have a different, more abstract concept of levels of reality. Here are some examples:
• You and I---or at least our bodies--- along with tables and chairs and cities and towns and planets. This is what philosophers call the level of medium size objects. This level of reality is what most of our lives are concerned with. The sorts of things we can perceive with our senses, and so forth.
• Contrast that with a level called quantum reality. Objects like quarks that we can’t see, having properties like spin that we can barely make sense of.
• On the level just above quantum physics, we find electrons and atoms; then there’s the level of chemical facts, where you have chemicals and bonds; then the level of biology, where you have cells.
• Higher levels too, like maybe involving minds, societies, nations…
• And there are angels and God… and numbers for that matter. So we’ve got lots of levels!
Intuitively each level has a characteristic kind of object, characteristic kinds of properties and facts, and usually a different profession for people that study or work with it: quantum physicists, solid-state physicists, chemists, biologists, psychologists, sociologists. Nearer the top, mathematicians and theologians. And then, at least according to Aristotle, at the very top: philoophers. He put philosophers there because we think about Being --- that is, the whole shebang, and we try to figure out how the different levels are related. Most contemporary philosophers feel more in the middle than at the top. And their approach to the issue of levels of reality focuses on the topic of reduction.

We can set God and the angels aside; philosophers who believe in them aren’t likely to suppose they are reducible to something else, and those who don’t believe in them don’t worry about their reducibility either. We can also set numbers aside, since neither Ken nor I have any firm ideas about them. Then, physicalists like Ken and I both tend to be, think that the rest must be one big reality, physical reality. Facts about chemicals really are just facts about atoms and electrons, and they are really just facts about subatomic particles, or whatever else turns out to be at the bottom. And the same with biology and chemistry; psychology and biology; sociology and psychology.
The divisions are based on how humans interact with the different phenomena, the tools we use, the interests we have, and, of course, the National Science Foundation budgets involved. and Ultimately, metaphysically, philohically, there is just one reality, matter in motion --- or whatever quantum physicists replace matter with, or whatever they replace motion with.
One might think of this as depressing and mysterious. I don’t feel like a complex of quarks. Of course, there is another theory. It’s the competitor to Reductionism. It’s called Emergence. That’s the idea that each level in some way emerges from the one below, under certain conditions. And when emergence happens, truly new objects, properties, and facts are involved.
One might favor reductionism over emergence on the basis that in some cases, the reductions though not yet discovered,  are in principle to be had.  Biologists have known since Mendel that something, which they called `genes', are responsible for inherited characteristics. But for a long time, there were debates about whether genes could really be explained by physical and chemical properties. Many biologists thought that genes could never be fully explained just in terms of physics and chemistry.   They thought, in other words, genes were emergent, and not reducible. But with the discovery of DNA and the development of molecular biology, we know this isn't so. The structure that Watson and Crick discovered has allowed scientists to explain how genes work without appealing to anything but the principles and properties of physics and chemistry.
If everywhere some philosophers see emergence, scientists will eventually provide reductions, emergence will just be another idea in the dust-bin called the history of philosophy. But that grand result would require a biological understanding of consciousness and all the other mental phenomena. Should would-be physicalists like Ken and I really be so confident of that? Is it so obvious that it even makes sense?
Luckily we have an expert on all of this to help us think about it, Tim O’Connor, author of Theism and Ultimate Explanation.