Thoughts about Free Will and Determinism from Mackie's Ethics Inventing Right and Wrong
 
Quotes from Ethics Inventing Right and Wrong, Penguin Books, 1990
 
Determinism says that what we choose is not really chosen for it is the result of many causes and it is the causes doing the "choosing" not us. Free will or indeterminism says we are not at the mercy of causes and can choose. Thus if you chose an orange a second ago, what if the universe took you back in time? If determinism is true then you will always choose the orange no matter how often you go back in time. Free will says you have the power to choose an apple instead or nothing or something else.
 
Compatibilism is the silly nonsense that determinism does not rule out us being free. It amounts to arguing that you can call the mere absence of being forced by people to act free will. Incompatibilism is the term he has for recognising that this is nonsense.
 
What does Mackie say about determinism?

One of the main arguments against such determinism appeals to a feeling or direct experience of freedom; whenever we choose to do one thing rather than another we are, in the experience of choosing, immediately aware that we could have done otherwise. But what sort of ‘could have’ is this? And is it an experience or just an assumption? We may dismiss the suggestion sometimes made by determinists that ‘I can…’ in such contexts means ‘I will… if I choose.’ A sounder thesis is that ‘can’ and ‘could have’ are used to deny obstacles and limitations of various sorts, and that it is not obvious what obstacles or limitations are being denied here; ‘could have’ need not be meant to exclude the sort of limitation that would be entailed by the action’s being (sufficiently) caused by a desire and that desire by further sufficient antecedent causes. It might well be used rather to deny obstacles and limitations external to the agent’s will at the time of the action. But such disputes about meaning are not very fruitful...

We can tell when an action results from and is guided by a desire. By contrast, one could be aware of an action which seemed not to be initiated or guided by any desire, but this would surely be the experience of doing something automatically, non-voluntarily, and it is not this that indeterminists mean by a feeling of freedom. Again, one can have the experience of desires arising as it were from nowhere, from no known causes; but this is not a positive experience of their being uncaused.

Comment: You can fake the feeling of freedom. You can even feel you don't exist. The feeling tells you nothing.

It is true that if you think you do an action without being prompted by a desire this may not be evidence that you have free will because it could be automatic and have nothing to do with your will. The notion that you have actions that to your psychology are uncaused does not prove they are uncaused. An uncaused action will feel the same as an automatic or non-voluntary one. It could be that something non-voluntary is making you think desires and causes are not giving you your actions. Determinism and its opposite are seen by many as being equal opponents of free will. This would prove that free will is incoherent rubbish.

Religion says that we are free because of God and not in spite of him.  So God then in a sense is choosing when we choose.  As it is us choosing to create sin not him religion says he is not sinning when we sin.  So then we are not free because of him after all.  This doctrine shows that incredibly belief in God refutes the argument that you are free for you can feel it.  We feel we really do defy God so if that is wrong feelings are good for nothing.

Plus if I experience that I have done something in a disconnected way, my action did not come from me really.  So it must be God is to blame. 

Another argument is that determinism would undermine rational judgement, and hence that we could not both seriously adopt a belief and see our adoption of it as causally determined. But the premise is false: it is not being causally determined in general that undermines a belief and deprives it of authority, but only being causally determined in an inappropriate way. There would be no difficulty in seeing (some of) our beliefs as arising causally but in appropriate ways, ways likely to keep them in accord with reality, and continuing to hold them seriously. And (as Norman Malcolm has argued) even if the premises were true what it would show is that determinism could not be rationally accepted, but might none the less be true.

Comment: Good! The bad results of belief x or fact x have nothing to do with proving them false.
 
I would wonder though about what happens if you assume that God sets all things up. If God is good then he helps us develop beliefs. Then a belief having terrible results or potentially bad results means it is false. This would ruin philosophy and is clear proof that belief in God has to go.

Hard determinism is the view which combines determinism with incompatibilism, and concludes that our judgements about responsibility and the like must be radically revised; soft determinism is the union of determinism with compatibilism. Those who reject determinism usually are, though they need not be, incompatibilists; this combination constitutes voluntarism or the doctrine of free will.

Comment: Some messing around here with definitions. There are only three. Determinism is when the causes "choose". Free will is when you choose not the causes. Compatibilism simply tries to claim that if you are determined and nobody outside you is forcing you that is free will. It redefines. 

Compatibilism is never able to tell us how you can be programmed and still free. To say we are partly one and partly the other is to say that determinism is true and free will is also true and they co-exist and are compartmentalised in the person. But compatibilism fuses them and the end result ends up being ridiculous. Determinism is the simplest and most straightforward hypothesis. It is the default so it has no burden of proof. Free will has a burden of proof but compatibilism has a bigger one for it is trying to portray a contradiction as making sense.

People should care enough about each other to give evidence for what they believe or think they know.  Nobody tries to give you evidence for free will.  This happens with those who affirm free will and the confused version of free will that you see from compatibilist writers.

MACKIE: Courage ... is a kind of strength. It makes its possessor more likely to achieve whatever he sets out to do, whereas the foolhardy man is likely to destroy himself or his enterprise or both, and the timid man is too easily turned aside.

Comment: All unselfish people start off on courage. They stir up strength in themselves. But it is their strength and their possession so they are not so unselfish after all. They are like those who pour themselves a bath to languish in and say that it is so that others may find them clean and fresh.  This quote should have told Mackie that what is upheld as virtue is in fact self-interested.  There is no free will then to put God-interest or other-interest in the place of self-interest.  So there is no useful doctrine of free will. 

I wish to say finally that the lies and distortions that are needed to affirm personal responsibility are clear proof that ethics is based on fantasy just as the title of Mackie's book implies.