When looking at free will, we must first have an agreement on the precise definition of the term in question. I define free will as the ability to make a decision or do an action not indicative of basic survival requirements, innate drives, or past experiences. I believe that free will is an illusion that a mind creates for the purposes of survival. An example of something by this definition that is not considered free will is eating for survival, without yet exploring the nuances of food choice and amount, the primary reason to eat is for a human's survival, I'm sure we can agree that a rational human without any mental issues (Ill touch up on this subject later) would eat in order to survive, Thus by definition a humans desire to eat indicates a lack of free will because it is a basic requirement of life that must be achieved. I would go as far as to say that the key reason for all actions a human does that, they believe is free will be tied back to an innate function that all humans must do to stay alive. These innate functions being, the gathering and consumption in one way or another of sustenance to stay alive, sleep, and comfort (meaning temperature of the body, mental pain, physical pain etc...).
Starting with my original example, let's say a man decided to eat something. He doesn't this for a few reasons but most likely it because he is hungry. Him deciding to eat something is the result of his body sending signals indicating his need for food to the brain. Let's say he decided to eat a steak and a potato, as a random example, the food choice is simply based of what ha seems would fit his appetite best, your appetite is just your body telling you what sounds good to eat to encourage you to eat. If he doesn't choose to eat because he has a mental condition such as anorexia, it's still his body's reaction to past events and traumas that he is basing his eating habits off of. It shifts the goalposts in a way were his brain sees not eating food as important as or more important than eating, it's still his brain telling him what to do based of its reaction to the environment and his past experiences not free will. Someone might say a man could go against survival needs in ways like fasting, but that would be explained by a human chasing deeper values which were instilled by the world around them, while this may appear as freedom it is the brain trying to do its best to do what it thinks is most important for survival, such as life after death in religious connotation.
A much more extreme example, if this man jumps from a building killing himself, was that free will? The answer is no, he most likely threw himself from the building do to mental pain that he is experiencing, his brain takes in the feedback, comes up with a solution and that solution is to jump, no point in that timeline did he have free will, every decision made from him decided to kill himself, to jumping was based off of what his brain understood as the best way to fulfill his innate desire of mental comfort.
Therefore, human behavior follows the rule that all choices are based of biological imperatives, mental states, and prior experiences. By this reasoning free will does not exist.
