The determinism and justice paradox

when I came across determinism and the possible absence of free will, the whole idea just blew me away. The thought that none of our actions are freely willed but a consequence of previous events was bewildering. But the initial bewilderment was followed by lots of doubts and a sense of inevitability in our lives. Why then do what we do? why do anything? I was able to answer most of them by claiming it is an illusion we can't get rid of, we're so bound by it and the feeling of inevitability is also not free! The choice of not doing anything is also not a choice, by the same reasoning. So, might as well live with the illusion of doing stuff that we feel like doing. One major doubt I had then was the futility of reward and punishment in the absence of free will. Why reward or punish someone when he wasn't really free to make the choices that he did make. I initially had to answer that too with the simple answer of it being an illusion.

But, as I thought again I begin to realise that while the part of illusion might answer why we reward or punish, but the benefits of reward and punishment aren't really bound to free-will. All it requires is a learning mechanism which uses feedback from past outputs to alter the system transfer function, something similar to a neural network (which is modeled from our own brain!). Any feedback mechanism which gives more weightage to those actions that result in a positive response and less weightage for those actions with a negative response would benefit from rewards and punishments. It doesn't require free will. As I think about it a bit more, I begin to realise that a punish and reward mechanism is precisely what is required in the absence of a free will. A free will that is un-influenced by external causes would be totally immune to any form of punishment or reward. It is because that our will is not free that we can learn from our mistakes, as they become a part of what makes "us" just as much as our accomplishments.