The Illusion of Sugar's Sweet Taste

Sugar's sweet taste has absolutely zero effect on your having a second bowl of ice cream. Particular receptors had to evolve in tongues and certain ideas encoded in brains for that to follow. People are just doing things because the laws of physics determine they will. But what if you as a person did things because you wanted to? What if that was the true explanation? If it really is not, then your wanting anything has no effect on what happens. And at the level of physics, what if it's possible for you to literally create an idea in your head? Like how about I have another bowl of ice Cream?