b) To what extent was Hume successful in his critique of the cosmological argument? 
Hume makes some very important challenges to the Cosmological argument which some believe count decisively against it. One of the key areas he calls into question is the argument’s dependence upon what Leibniz termed the principle of sufficient reason. In this principle an adequate explanation must be a total explanation. The universe requires an explanation of itself as a whole. But many would say, as Russell later told Copleston: “Then I can only say that you’re looking for something which can’t be got, and which one ought not to expect to get.”
If you have explained each individual element of a series any explanation of the series as a whole would seem to be superfluous, and besides he says that ‘the whole’ doesn’t really exist anyway – it is ‘an arbitrary act of mind’ that makes things into wholes. What we term the ‘whole universe’ in modern physics may be only a bubble in a larger reality that we have no way of grasping. Also if we are only entitled to talk about causes when we have had experience of them, then this argument would seem to be over-stretching itself in speculating upon what it cannot know.
On the other hand, there is of course a problem with stopping at a certain point and saying that we should seek no further explanation, in that it is a basic presupposition of all scientific work. However, even though a principle of rationality is that we can find an explanation for things, it is not a logical requirement – there is no guarantee that there will be one. So, I think Hume significantly weakens forms of the argument that depend on the principle of sufficient reason.
However, I think that Hume’s criticisms of a necessary being somewhat misunderstand what is meant by necessity in this case. Some have said that this argument arrives at a factually necessary being, not a logically necessary one, so that Hume’s point that any being may or may not exist is question-begging because the argument seems to arrive a posteriori at a being that has to exist.
Hume has outlined some powerful problems with the argument, but they do not totally defeat it. I think we are at least entitled to ask the question of what caused the universe, as this is what modern physics does. The difficulty is in arriving at the Christian God as an answer to such a question. I think therefore that Hume was fairly but not completely successful in his criticisms of the argument.
Breakdown of part b answer:
Key phrase: “To what extent…” Envisage this as a matter of degree. Try rephrasing as ‘how much’ or ‘how far’ or ‘how successful was Hume’ in challenging the argument? Did he deliver a knockout blow? If so what was it? Why was it a KO? If he didn’t did he only daze the argument so it stills stands, or is it down on one knee? If you visualise the problems and the criticisms like that you won’t finish the essay without doing some kind of evaluation.
1st paragraph: I begin by finding the most fundamental challenge to the argument and stating it. I think, along with many others, that there are fundamental flaws with the principle of sufficient reason, so any forms of the argument that rely on that will be severely challenged (Aquinas’ Third Way does of course). At the end of the paragraph I state an objection to it from Russell.
2nd paragraph: I briefly mention three other of Hume’s objections here. The fallacy of composition, the fact that the ‘whole’ is our own invention, epistemological scepticism. This paragraph is fairly explanatory, and does little evaluation, however, in the context of the essay, I feel it is necessary to establish Hume’s case a bit.
3rd paragraph: Where I make my evaluation of Hume, finding his challenge to the principle of sufficient reason powerful. This could have been improved with an example to show why I think this is the case. For instance, one of my students said that children playing hide and seek might be looking for a child who they presume is hiding. However, there is no guarantee that they will find the child, as he may have decided to go home. So also, the fact that you are looking for something doesn’t mean it has to exist. This kind of illustration is useful as it can help to persuade someone that there is a problem with an argument, by relating it to an everyday situation. In this case it also serves to illustrate what many see as the fatal flaw with the principle of sufficient reason. Notice that I also show why some think it is acceptable to seek a ‘total explanation’.
4th and 5th paragraphs : I was well over time by this point – you have 45 minutes to do part a and b, so you would only want 20 minutes maximum to do part b – I’m a slow writer/thinker, so find it challenging! Anyway, I finish off by mentioning where I think Hume is not so successful and concluding that I think his criticisms weaken the argument but not totally. I don’t really think my conclusion is completely supported by the body of the essay, but there you go, if I had more time I could!
Things I would have like to add:
More exploration of the fallacy of composition. Fallacies are useful things to find in arguments because they are errors of reasoning. For instance, where assumptions have been made, or a conclusion has been arrived at that doesn’t necessarily follow from the premise. They are useful because they can signpost that there is a problem with the argument, and they go beyond the kind of criticism that says “I don’t like this argument” or “I find it confusing”. Take the time to familiarise yourself with a list of fallacies on the internet, it will help when you come to evaluate any argument.
The fallacy of composition is an informal fallacy, and there are cases where it doesn’t hold – see this post here for an interesting viewpoint.