If free will does not exist -- i.e, each person is only an observer experiencing but never actually choosing or deciding anything -- can life still be meaningful?

This is an important question, since it might be that one of the reasons we worry about whether we have free will is that free will is required for life to be meaningful. If so, then any threat to our free will would also make life meaningless. (Actually, as I write that sentence, it makes me wonder if a person's life can only be meaningless, in the ordinary sense of that word, if it has a possibility of being meaningful--is a worm's life meaningless or does that word simply not apply?) But is free will required for life to have meaning?

As usual (with philosophical questions like this), a lot depends on what we mean by 'free will' and 'meaningful life'. My own view is that a theory of free will needs to be about the powers of control that matter to us, so it doesn't make sense to define free will in such a way that losing it would not matter and such that having it would not matter. If, for instance, free will is defined as some magical ability to exist outside of the natural order of things, then I'm not sure why it would matter if we don't have it. But if, as you suggest, free will is the power to make choices and have your decisions make a difference to what happens, rather than just being a helpless bystander observing what happens, then it would be terrible not to have free will. And I find it hard to see how life could be meaningful without such free will, since it seems like part of what makes life meaningful is deciding what sorts of goals and plans you have and making choices that help you achieve those goals and plans.

I should emphasize that I am a compatibilist about free will and determinism (as I explain here), so I don't think that the truth of determinism would make life lack meaning because it would not make us mere observers whose decisions didn't make a difference. But figuring out how free will works is no easy task. And figuring out what makes life meaningful is even harder.

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