The second point makes it likely that consciousness is not simply a consequence of physics, but e.g. that it loops back into it; or perhaps it is more likely (because simpler) that physics is a consequence of consciousness.
You can never prove that there are others. Neither can you prove that there is a self. There is just consciousness, overlaid by various experiences, which we tend to attribute to a substantial self. So it doesn't make sense to ask for a proof that others have consciousness, until you can define self/others properly.
> Why would something that has no consciousness make up that it has consciousness?
You can make a computer program `printf("I have consciousness\n");`
But I actually also didn't follow the rest of the argument. How does whether other people say they have consciousness or not, tell anything about whether it's physics based or not? If it's physics based, people could say they have consciousness. If it's not physics based, they could also say that?
2. This talking happens in the physical world (soundwaves are being produced, etc.)
3. We assume that other people have consciousness since they talk about it. As you say, there is no absolute proof of this, but Occam's razor makes it silly to assume otherwise.
4. So, the soundwaves (physics) are happening because of consciousness. There is a causal link from consciousness to physics.
This means that consciousness is not simply the observation of physics. It actually loops back into it, or physics is an emergent property of consciousness.
Not all sound is created that way, e.g. rain falling from the sky is not, do you intent to mean all physics, including rain, originate from consciousness in some way (such as in theories that everything is an illusion, ...), or rather, that consciousness can affect physics in some way, e.g. because you can choose to speak and produce sound waves
Unless consciousness is a property of matter at a certain point and then its physics that loops back into itself and consciousness is just a physical phenomenon.
1. you have consciousness
2. people are speaking about consciousness
The second point makes it likely that consciousness is not simply a consequence of physics, but e.g. that it loops back into it; or perhaps it is more likely (because simpler) that physics is a consequence of consciousness.