Yes I am aware. The issue is that in our current understanding we now know in chemistry we are adding element1+element2=element1+element2... (classically at lea

Yes I am aware. The issue is that in our current understanding we now know in chemistry we are adding element1+element2=element1+element2... (classically at least). So while Lavoisier led us to the above, the author is pointing to the fact that e1+e2=e1+e2 but to the reader this can be confusing because Lavoisier's Law also states the same... Though once you understand that you are just rearranging chemical bonds b/w elements there's nothing different about it. I don't have any intuition about how you would theoretically prove the assumption in Lavoisier's Law--Newton's 0th Law. It seems if Lavoisier's Law is true it implies Newton's 0 must also, at least intuitively... It's a reasonable source of confusion and I think it's ok the above poster was misguided about it as everyone agrees from the start on this: almost no one questioned such an assumption.