CTD (Circling the Drain) ... boy was he right.

Do we have free will? Are we puppets attached to strings (i.e. pre-destined)? If everyone has free will than no one can follow such a plan.

We do NOT have free will with the emphasis on the word free. Everything is deterministic and each of us is influenced by our environments, genes, brain chemistry, and experiences. However, we have volition which is the power to control our will that is bounded by all those factors. Volition is this free will that people commonly reference. Our volition and our desire to be above causality and nature is what make us human.
Free will is an illusion. In order to have free will then you must be able to make decisions without any outside influence causing you to make those decisions. You may have the subjective experience of this ability but it is not supported by reality, we live in a universe of cause and effect. You make your decisions based on who you are and who you are is ultimately determined by your genetics and what you have learned from the environment that you were born into. These two factors of nature and nurture determine who you are and you did not choose your genetics or the environment that you were born into. So if you follow the causal chain of your decisions backwards to the source you will end up outside of yourself. The more we learn about Neuroscience and Psychology the more evidence we have of this reality.

In Neuroscience the prime example is the Libet experiments and the many variations thereof. The experiment can be summarized as the subject being hooked to some kind of brain scanning device, such as a fMRI machine, and then asked to make a decision while watching some sort of clock or series of images to mark the time in which the decision is made. When the brain scans are compared to the moment in time the subject made the decision in consciousness it is shown that the decision was already made in the brain before it was made in consciousness. The experience of making the decision is only the conscious witness of the decision being made in the physical system and not the actual cause of the decision.

In psychology there are many examples as well, one of them being the hungry judge study. In this study it was shown that an inmate's chance of being paroled is greatly determined by how long it has been since the judge has last eaten. The data shows that an inmate is about 65% more likely to receive a favorable decision from the judge after the judge had eaten and nearly 0% just before the judge takes a break for lunch only to rise back up to 65% after he returns from his break. Now of course the judge would not say that his decision was determined by how hungry he was but that is what the data shows. There have been similar studies done on how tired the judge was affecting his decision and with similar results. Other studies show how a person's behavior can be affected by something as trivial as the temperature of the drink they are holding in there hand where a person was more likely to be generous and cooperative if they were holding a warm drink versus a cold drink. When asked to explain people will come up with ad hoc excuses for their behavior but the data shows that it was determined by other factors.

So we are making decisions and acting in ways that are being determined by factors that we are not even aware of. If we do not even know why we are making these decisions or if our decisions do not even originate in consciousness how can we say we are making them of our own free will. A will is not free if it is being determined by outside influences. The reason why I think it is important is because our criminal justice system focuses on retributive justice based on the concept of free will. I believe it is immoral to take revenge on a criminal for something they ultimately were unable to control. Instead we should focus on rehabilitation and providing deterrents to prevent future criminal activity and not taking revenge for past criminal activity. So for example the death penalty has not shown to provide a stronger deterrent than life in prison and it has proven to be more expensive mostly due to legal fees. The only real reason for the death penalty is to enact revenge on the person who committed the crime. I would say this is immoral, especially in the absence of free will.

If I were inclined to follow anyone's teachings, it would've been Carlin's

Carlin was right FAR more often than he wasn't.
People still don't understand, or want to acknowledge, that he was right about
nearly everything.