@jessicata once wrote “Everyone wants to be a physicalist but no one wants to define physics”. I decided to check SEP article on physicalism and found that, yep, it doesn’t have definition of physics:
Carl Hempel (cf. Hempel 1969, see also Crane and Mellor 1990) provided a classic formulation of this problem: if physicalism is defined via reference to contemporary physics, then it is false — after all, who thinks that contemporary physics is complete? — but if physicalism is defined via reference to a future or ideal physics, then it is trivial — after all, who can predict what a future physics contains? Perhaps, for example, it contains even mental items. The conclusion of the dilemma is that one has no clear concept of a physical property, or at least no concept that is clear enough to do the job that philosophers of mind want the physical to play.
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Perhaps one might appeal here to the fact that we have a number of paradigms of what a physical theory is: common sense physical theory, medieval impetus physics, Cartesian contact mechanics, Newtonian physics, and modern quantum physics. While it seems unlikely that there is any one factor that unifies this class of theories, perhaps there is a cluster of factors — a common or overlapping set of theoretical constructs, for example, or a shared methodology. If so, one might maintain that the notion of a physical theory is a Wittgensteinian family resemblance concept.
This surprised me because I have a definition of a physical theory and assumed that everyone else uses the same.
Perhaps my personal definition of physics is inspired by Engels’s “Dialectics of Nature”: “Motion is the mode of existence of matter.” Assuming “matter is described by physics,” we are getting “physics is the science that reduces studied phenomena to motion.” Or, to express it in a more analytical manner, “a physicalist theory is a theory that assumes that everything can be explained by reduction to characteristics of space and its evolution in time.”
For example, “vacuum” is a part of space with a “zero” value in all characteristics. A “particle” is a localized part of space with some non-zero characteristic. A “wave” is part of space with periodic changes of some characteristic in time and/or space. We can abstract away “part of space” from “particle” and start to talk about a particle as a separate entity, and speed of a particle is actually a derivative of spatial characteristic in time, and force is defined as the cause of acceleration, and mass is a measure of resistance to acceleration given the same force, and such-n-such charge is a cause of such-n-such force, and it all unfolds from the structure of various pure spatial characteristics in time.
The tricky part is, “Sure, we live in space and time, so everything that happens is some motion. How to separate physicalist theory from everything else?”
Let’s imagine that we have some kind of “vitalist field.” This field interacts with C, H, O, N atoms and also with molybdenum; it accelerates certain chemical reactions, and if you prepare an Oparin-Haldane soup and radiate it with vitalist particles, you will soon observe autocatalytic cycles resembling hypothetical primordial life. All living organisms utilize vitalist particles in their metabolic pathways, and if you somehow isolate them from an outside source of particles, they’ll die.
Despite having a “vitalist field,” such a world would be pretty much physicalist.
An unphysical vitalist world would look like this: if you have glowing rocks and a pile of organic matter, the organic matter is going to transform into mice. Or frogs. Or mosquitoes. Even if the glowing rocks have a constant glow and the composition of the organic matter is the same and the environment in a radius of a hundred miles is the same, nobody can predict from any observables which kind of complex life is going to emerge. It looks like the glowing rocks have their own will, unquantifiable by any kind of measurement.
The difference is that the “vitalist field” in the second case has its own dynamics not reducible to any spatial characteristics of the “vitalist field”; it has an “inner life.”
It’s not surprising that a lot of people don’t want to define physics while believing in physicalism, because properly explaining the equations that describe the physical world would take quite a long time, let alone describing what’s actually going on in physics, and it would require a textbook minimum to make this work.
I feel like one should use a different term than vitalism to describe the unpredictability, since Henri Bergson cane up with vitalism based on the idea that physics can make short-term predictions about the positions of things but that by understanding higher powers one can also learn to predict what kinds of life will emerge etc..
Like let’s say you have a big pile of grain. A simple physical calculation can tell you that this pile will stay attached to the ground (gravity) and a more complex one can tell you that it will remain ~static for a while. But you can’t use Newtonian mechanics, relativity, or quantum mechanics to predict the fact that it will likely grow moldy or get eaten by mice, even though that will also happen.
A definition of physics that treats space and time as fundamental doesn’t quite work, because there are some theories in physics such as loop quantum gravity in which space and/or time arise from something else.
@jessicata once wrote “Everyone wants to be a physicalist but no one wants to define physics”. I decided to check SEP article on physicalism and found that, yep, it doesn’t have definition of physics:
This surprised me because I have a definition of a physical theory and assumed that everyone else uses the same.
Perhaps my personal definition of physics is inspired by Engels’s “Dialectics of Nature”: “Motion is the mode of existence of matter.” Assuming “matter is described by physics,” we are getting “physics is the science that reduces studied phenomena to motion.” Or, to express it in a more analytical manner, “a physicalist theory is a theory that assumes that everything can be explained by reduction to characteristics of space and its evolution in time.”
For example, “vacuum” is a part of space with a “zero” value in all characteristics. A “particle” is a localized part of space with some non-zero characteristic. A “wave” is part of space with periodic changes of some characteristic in time and/or space. We can abstract away “part of space” from “particle” and start to talk about a particle as a separate entity, and speed of a particle is actually a derivative of spatial characteristic in time, and force is defined as the cause of acceleration, and mass is a measure of resistance to acceleration given the same force, and such-n-such charge is a cause of such-n-such force, and it all unfolds from the structure of various pure spatial characteristics in time.
The tricky part is, “Sure, we live in space and time, so everything that happens is some motion. How to separate physicalist theory from everything else?”
Let’s imagine that we have some kind of “vitalist field.” This field interacts with C, H, O, N atoms and also with molybdenum; it accelerates certain chemical reactions, and if you prepare an Oparin-Haldane soup and radiate it with vitalist particles, you will soon observe autocatalytic cycles resembling hypothetical primordial life. All living organisms utilize vitalist particles in their metabolic pathways, and if you somehow isolate them from an outside source of particles, they’ll die.
Despite having a “vitalist field,” such a world would be pretty much physicalist.
An unphysical vitalist world would look like this: if you have glowing rocks and a pile of organic matter, the organic matter is going to transform into mice. Or frogs. Or mosquitoes. Even if the glowing rocks have a constant glow and the composition of the organic matter is the same and the environment in a radius of a hundred miles is the same, nobody can predict from any observables which kind of complex life is going to emerge. It looks like the glowing rocks have their own will, unquantifiable by any kind of measurement.
The difference is that the “vitalist field” in the second case has its own dynamics not reducible to any spatial characteristics of the “vitalist field”; it has an “inner life.”
It’s not surprising that a lot of people don’t want to define physics while believing in physicalism, because properly explaining the equations that describe the physical world would take quite a long time, let alone describing what’s actually going on in physics, and it would require a textbook minimum to make this work.
I feel like one should use a different term than vitalism to describe the unpredictability, since Henri Bergson cane up with vitalism based on the idea that physics can make short-term predictions about the positions of things but that by understanding higher powers one can also learn to predict what kinds of life will emerge etc..
Like let’s say you have a big pile of grain. A simple physical calculation can tell you that this pile will stay attached to the ground (gravity) and a more complex one can tell you that it will remain ~static for a while. But you can’t use Newtonian mechanics, relativity, or quantum mechanics to predict the fact that it will likely grow moldy or get eaten by mice, even though that will also happen.
A definition of physics that treats space and time as fundamental doesn’t quite work, because there are some theories in physics such as loop quantum gravity in which space and/or time arise from something else.
To be fair, basically a lot of proposals for the next paradigm/ToE think that space and time aren’t fundamental, and are built out of something else.