Some rough notes from a personal attempt to clarify my own thinking. Consider this a work-in-progress and probably wrong.
Principles underlying feeling of freedom of will (note that this is different from freedom of action or actual agency):
- Bayesian updating (distribution of decisions)
- State/neural dynamics are unpredictable in the future
- Accessibility of internal state
- Web of concepts
- Feedforward-ish network
What is it that makes someone believe themselves to be free? That they can exercise willpower in pursuit of moral agency?
There are a few concepts from neuroscience that we want to understand for the feeling of freedom in a deterministic world.
The first concept we have to understand is that the brain is a neural network. It has neurons connected to other neurons connected to other neurons. We like to imagine them as step-by-step programs that slowly process information and allow an organism to make a decision but in reality they are vastly interconnected. Still, there is some validity to levels of feedforward-ness! The important thing is that not every neuron has access to the information from every other neuron – and not every ‘layer’, or collection of neurons, has access to information from every other ‘layer’.
The second concept is that the brain is interested in the fundamental unpredictability of the future. There are informational constraints on knowledge about what the internal state of a system will be, in both the sense of the current dynamics and the broader sense of ‘hunger’, ‘thirst’, ‘sleepy’, etc. Each of these modulates the activity of different layers of the brain in a variety of ways, often through neuromodulatory pathways. Further, as a corollary of this and the first concept, different layers have imperfect access to the state of other neurons and other layers.
The third concept is the implementation of ideas and memories as a web of concepts. Smelling an odor can transport you back to the first time you smelled it, with all the associated feelings. No idea exists in isolation but accessing one will inevitably access a variety of others (to a greater or lesser extent). This is foundational to how memories are stored.
The fourth and final concept is the Bayesian Brain, the idea that brains represent probability distributions and compute in terms of inference. No 19th century symbolic thinking for us – we process information in a manner that fundamentally requires us to think of the distribution of possible options or possible futures.
How does this give rise to a feeling of freedom of will? Suppose you were considering whether you were going to perform some action or not. When considering which of various possibilities you will take, there is some set of neurons making this consideration. These neurons do not have access to all of the possible neurons involved in the decision. In other words, these neurons do not know which possible action they will take. Instead they must operate on the set of probabilities for the future state of the network. The operation on this distribution is the feeling of free will – that there is an internal state, or internal dynamics, that are inaccessible from the consideration. These neurons get input from the dynamics and can plausibly provide output (the feeling of willpower).
Imagining the future is similar. Will I have the possibility of choosing freely among many options? Yes, of course, because I am unclear what my future state will be. The probability distribution conditional on external and internal state is not unitary (though it can be with properly powerful external stimuli).
Could I choose to eat bacon and eggs this morning instead of my daily bowl of granola? Possibly; it exists in probability space of possible options. Will I do so? I can sit there and sample my internal state and have some uncertainty about whether I desire that or not. That makes me feel free: I will choose to do so or not do so, unconstrained by outside forces, even though it is entirely deterministic.
Fundamentally, the feeling of freedom is a reflection of probabilistic and uncertain thinking.