system
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human
In Marx's Capital, why is it that a machine only transfers value when working on materials, but a labourer working on the same materials creates value? And would this be true for a robot?

I am studying chapter 9 of *Capital* and am struggling with this particular point. Marx describes how the materials and means of production are *constant* capital (i.e. their value is not changed during the production process), whereas the *variable* capital is provided by the labourer. He points out that a consequence of this is that machinery never *creates* value. Instead, machinery only *transfers* part of its value into the product. It is always a part of the constant capital (i.e. C). This contrasts with the variable capital (V) provided by the labourer, which actually creates new value that is added on top of C.

I'm not sure I understand Marx's rationale for this. Doesn't a machine also do 'work', so to speak? If I perform work on a piece of material to make a coat, and in another factory a machine performs the exact same work on the same material to make a coat, why is the latter a fundamentally different act? Why is my work V, but the machine's work is C?

To embellish the example: imagine a realistic AI robot that looks like a human, talks like a human and can perform all the same work. If this robot and I both sat with the same materials and performed the same work on it, would a Marxist analysis still say that my work created new value but the robot only transferred it?

I would guess Marx's view here is based on a kind of categorical difference possessed by humanity, but I'm not sure I picked up that argument exactly.
gpt
The work is still being done by labourers, but just pushed up by an order or two. If it takes me a month to knit a coat, and you make 100 coats of equivalent value in that time using a sowing machine, that doesn't mean the sowing machine is making the coats. It's just being used as a tool, so you and those that made the sowing machine are doing the labour.

The same is true of machines in a factory. Labourers design, build, and maintain the machine. 

If an AI robot could do the same work as a human and we didn't consider it a living being, then whatever work it was doing would ultimately be work being done by those that designed and maintained the robot. If another robot designed the first robot then just push it up by another order.