The main result of thermodynamics is that if you have a place that is hot and another place that is colder, you can operate a heat engine by absorbing heat from the hot place and dumping it in the cold place, extracting some useful work in the process. It gives you a way to calculate the maximum possible useful work per unit heat absorbed from the hot source. Thermodynamics doesn't seem to care whether you actually do extract some useful work from the tendency of heat to flow from hot to cold. It allows for maximally irreversible processes, such as the free expansion of a perfect gas. If you start with a gas initially confined to one half of a container, and then remove the partition, it fills the whole container without doing any work. That is a squandered opportunity to extract work that the universe will never get back. So how is it that the universe actually does use temperature differences, voltages, chemical potential gradients, and so on to do work--to create structures? What stops the universe from being maximally wasteful, letting all differences simply smear out, without generating any structures along the way?