John Stuart Mill famously remarked that labor-saving machines have not saved one minute of labor. More seriously, Marx argued, roughly, that machines can gain temporary market advantage, but cannot produced "surplus value," which come only from increasing attachment of labor. (Though Marx's value theory is complex and slightly ambiguous.)

Nonetheless, observers, neoliberal and socialist alike, seem to agree that machines are "productive" and "labor-saving" overall. For neoliberals this is productive "innovation" and for leftists "technological unemployment." The idea of a future where "most work is done by robots" seems remarkably widespread. This strikes me as a fallacy for three reasons.

First, in a rough adaptation of Say's Law, someone must obviously make, fuel, and maintain the machines. Someone else must, for example, mine the additional metals, feed the miners who mine the metals, raise the farmers who feed the miners who....etc.

Second, the rise of "labor-saving technology" since the 19th century has come with a huge, five-fold increase in the global laboring population. The "local" increases in per-laborer productivity appear more than offset by the attachment and utilization of increased, lower-cost labor worldwide.

Third, the idea of "robots doing all the work" would seem to violate the Second Law of Thermodynamics. Machines cannot run or reproduce themselves. The only "perpetual motion machine" is life itself. Without humans all machines succumb to entropy almost immediately. This would apply to any level of technology.

I am not arguing that machines make no difference. But is this difference primarily local and conditional? Is the local "productivity" of machines primarily and irreducibly a way of displacing labor globally... and redirecting labor through "machines" from lower-cost to higher-cost zones?

Above all, is it logically possible for machines to produce more "work" in total than goes into them? Again, even apart from issues about "quality of work," I am always surprised at how many people seem to assume this "robot replacement scenario" is plausible.

P.S. Though I would like to respond to answers and comments, the "comment" function is not working for me at the moment, I have asked "Help" about it. My argument from thermodynamics appears to be misunderstood, I will address as soon as possible.

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    $\begingroup$ It appears to me that although you write about the fallacy of "most work done by machines" (my emphasis), the first and third arguments pertain to "all work done by machines", and this is a critical qualitative jump that renders them irrelevant. $\endgroup$ Commented Nov 18, 2015 at 13:14

3 Answers 3


The only "perpetual motion machine" is life itself.

No it is not. We also convert energy to heat as we go through life. We are certainly not immune to the second law of thermodynamics, we increase entropy all the time.

Machines cannot run or reproduce themselves.

Why not? There is already factory robots making other robots. But of course, they run on fuel. But again, humans also run on fuel, we just call it food.

[...] someone must obviously make, fuel, and maintain the machines. Someone else must [...] mine the additional metals, feed the miners who mine the metals, [...]

Yes, there is a kind of dependency graph, and for now there are many spots for humans, there are many things the machines just cant do. But there are no fundamental reason why a machine can't fix another machine, and there is no reason why there can't be a "universal repair machine" which also repairs copies of itself.


Only thing you need to realize I think is that humans are machines, very lousy and inefficient machines at that.

Once you accept that, then it becomes evident that at some point we will be able, at worst, to create a replacement to human at lower cost.

Realistically what will be produced isn't an exact replica, but rather, a machine with all the upsides and none of the downsides that will be able to out-perform human at anything.


The laws of thermodynamics and futuristic technological advancement aside, I will attempt to answer the economics portion of the question.

You are a farmer that needs to plant "the back forty" (acres). You could either (A) use a hoe and do the work by hand, or (B) use a tractor and do the work in a matter of hours. You would probably choose the tractor since it would save you weeks of labor that you could use to work another job or till more acres of land.
You chose to use the machine because it reduced your labor.

But what about the labor beyond your local farm? Any farmers around you who do not have a tractor will not be able to keep up with your productivity. The market disruption will force them to sell their farms and, more importantly, find work elsewhere.
No one is going to pay them because you have a tractor or because technology has advanced beyond hoes. The other farmers are still going to need to work for their living.
So, they go find work. Fortunately for them, the invention of tractors has caused a small increase demand for iron chassis, rubber wheels, petroleum, etc. and new jobs have been created.
Some of the farmers get these jobs; the rest of the farmers get jobs in other sectors of the economy. These ex-farmers invent or help to invent other machines, and the cycle continues.

Did the ex-farmers' transition from a "low-cost" zone to a "high-cost" zone?
I would answer with "a qualified yes." The ex-farmers could no longer make a living as farmers. So they moved to a sector where they could make a living. However, I would also say that the invention of the tractor transitioned the farmer occupation from a "high-cost" zone to a "low-cost" zone, in the first place.

Is it possible for the tractor to produce more "work" in total than goes into it?
Yes. Since it is much harder to see this answer from the tractor example, I will used the simpler "machine" of the lever.
You are using your tractor to plow some new land and find a 200lb stone in your field. You do not have rope to pull it with the tractor; instead, you use a sturdy tree branch to move the stone. Depending on how long your lever (tree branch) is and where you place your fulcrum, any amount of force less than 200lbs would move the stone.
The equation for the lever is $F_1 * d_1 = F_2 * d_2$ where $F_1$ is the 200lb stone, $d_1$ is the distance of the stone to the fulcrum, $F_2$ is your force, and $d_2$ is the distance of your force to the fulcrum. If we assume that $d_1 = 1 ft$ (for simplicity), we have the equation become $200 = F_2 * d_2$.
If your distance to the fulcrum ($d_2$) is 2 ft, you will need to apply 100lbs of force.
If your distance to the fulcrum is 4 ft, you will need to apply 50lbs of force.
This validates our answer that, yes, it is possible to get more work out of a machine than is put into it.


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