I once asked in the Physics Stack Exchange what the definition of a machine is. I did not really get a good response. Now, I am trying the philosophy stack exchange, as philosophy deals with coming up with definitions of things. How does one define whether a physical system P is a machine? For example, I think most people would agree that an atom is not a machine. I am also interested in what philosophers have thought about the topic of machines and coming up with possible definitions that capture our intuition as best as possible.

Edit: The main reason I am asking this question is because I want to know whether humans and other animals (and also other biological organisms like plants and bacteria) are machines. People like Richard Dawkins claim that living things are machines, but to know if that is really true, we need a definition of machine.

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    Something that may be important for the discussion is why you want a definition of a machine. Often the definitions are tailored to what one is doing with the ideas after they are defined.
    – Cort Ammon
    Commented May 18 at 22:18
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    I find it puzzling you didn't get a good definition, since physics has a simple notion of machine that includes the screw, plane, pulley, etc. See teachengineering.org/populartopics/simplemachines . Also, WP has a number of definitions: en.wikipedia.org/wiki/Machine
    – J D
    Commented May 18 at 22:21
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    I’m voting to close this question because this is more a question of conventional definition than philosophical disputation.
    – J D
    Commented May 18 at 22:22
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    However you want. Like most words, machine means a host of related but incompatible things already, and anybody can come along and define a new meaning if they think it's useful at the time.
    – g s
    Commented May 18 at 22:56
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    Are living things considered machines? Yes and no. Is beer a good thing to drink? Yes and no. Well, now that we've got that out of the way...
    – Scott Rowe
    Commented May 19 at 15:11

1 Answer 1


As I mentioned in comments, the goal of the definition of "machine" is important. In your edit, you state the goal is to determine whether a living thing is a machine or not. This is actually somewhat backwards. Is a living thing a machine? Sure why not. Or no.. why not. Either way. "Machine" is a word, nothing more. On its own it means nothing and we are free to define it to include or exclude living things at will.

Of course, language is not in a vacuum. When we try to define words like "machine," we're trying to assign a precise meaning to something intuitive. In our case, we have a concept of a "machine," and how we interact with them. A definition that is consistent with that is a useful definition.

Richard Dawkins claims living things are machines because it is useful for him. If he can convince you to use your intuitive definition of "machine" for living things, it supports his arguments.

One thing we can do is apply model theory. If Richard Dawkins says "living things are machines," that binds how he can use "living things" and "machines" in the rest of his argument.

Now, all that aside, there's some physical meaning that I'd assign to "machine" which is common enough to be neccesary conditions: all machines should have these (in my opinion), but may not be sufficient to call something a machine.

  • Machines have predictable behaviors. You can determine what it will do in an environment before putting it in that environment.
  • Machines can be constructed. Given some "raw materials," one could construct a copy of a machine.

Now something less agreed upon would be whether machines have freewill. Generally speaking, we tend to assume that machines do not have freewill. That comes with gargantuan implications if one claims humans are machines.

Now is this all clear? Maybe not. Consider Arthur C. Clarke's famous quote: "Any sufficiently advanced technology is indistinguishable from magic." As machines get complicated (and if humans are machines, they are certainly quite advanced technology), the line between machine and magic gets blurry. Words like "magic" are typically used in a way that is compatible with things like "free will."

I like this quote because it doesn't claim that a machine is magic. It claims that it is indistinguishable from magic. And that suggests that even if a human is actually a machine, it might be indistinguishable from something magical. This delves into the difference between ontology and epistemology. Whether there is a true answer to "are humans machines?" or not, we may be able to argue that there is no way to know the answer.

For a non-philosophical answer, I'd like to plug an answer on Worldbuilding that I'm quite proud of: What's the smallest change to physics required to allow magic?

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