Not every change in material resources is a change in supply. For example, the rate at which the Sun burns energy is not controlled by humans, nor even known to us. However, the Sun’s energy will effect demand nonetheless—ice cream will become more popular if the sun heats up, and it will be purchased more often. Thus the sun is a counterexample to the claim that changes in demand are all the result of changes in supply.
You might claim that the change in ice cream demanded is actually the consequence of increased ice cream production. That is true in the sense that if no more ice cream was produced then no more ice cream would be consumed. But we can also ask what caused the company to choose to increase production, and the clear answer is that the company increased production because they thought the demand for ice cream would increase. Heat itself is meaningless except in its anticipated consequence for demand, therefore the counterexample is valid.
Okay, thought things through.
Not every change in material resources is a change in supply. For example, the rate at which the Sun burns energy is not controlled by humans, nor even known to us. However, the Sun’s energy will effect demand nonetheless—ice cream will become more popular if the sun heats up, and it will be purchased more often. Thus the sun is a counterexample to the claim that changes in demand are all the result of changes in supply.
You might claim that the change in ice cream demanded is actually the consequence of increased ice cream production. That is true in the sense that if no more ice cream was produced then no more ice cream would be consumed. But we can also ask what caused the company to choose to increase production, and the clear answer is that the company increased production because they thought the demand for ice cream would increase. Heat itself is meaningless except in its anticipated consequence for demand, therefore the counterexample is valid.