There’s an esoteric school of thought which maintains that we aren’t who we think we are. We think of ourselves as an integrated individual personality but this theory suggests that we are a actually a number of different “I’s” that occupy the same physical body (like but not as a multiple personality) and that different “I’s” take over control of the organism at different times, so that the decisions made at one point are often countermanded when another “personality” takes control of the apparatus.
Think of it this way: When you are coming on to someone you are attracted to, one personality takes over. When you are confronted by drunk on the street, a very different personality takes over. You are one person at work, and quite another person at home with your family, and if this isn’t true, you’re in a lot of trouble if you behave in exactly the same way at work and at home.
So, when you ask the question, “Why choice A instead of choice B?” you first have to ask yourself who is in charge? Is it the weight conscious person who decides not to order the cheesecake, or the guy with the sweet tooth who just has to have that cheesecake?
There another ontological problem called the law of inevitable consequences, which I just made up. As we age, our free will becomes progressively more constrained by education, experience, and levels of wellness.
When I was 15, I could have decided to become doctor or a cop. At 40, there is no possible way I could ever become a doctor because I wouldn’t have enough years left to complete my medical education and pay off my student debt, but I could still become a cop, put in 20 years, and retire at half-pay at age 60. At age 60, however, no one would hire me to be a cop because I couldn’t put in enough years to qualify for a pension. I would be just as competent at 60 as any other 60 year old would be with the proper training, but the pension is an integral part of police culture and no one would want to work with a cop who was never going to be able to qualify for a pension because that person would be regarded as unreliable since he or she didn’t have that pension to protect.
Every decision we make in life has the effect of either expanding or reducing our future options. As we age, the percentage of decisions that increases our future options decreases while the percentage of decisions that decreases our future options increases. In this respect, there really is no such thing as pure free will. We are always constrained by gradually more restrictive circumstances.