I accused him of simply doubting this idea, without giving any argument for his rejection of such an obvious position–that is otherwise the basis of all rational inquiry. To be fair to Mackie, that isn’t quite right. He does offer some counter explanations, and a more rational objection.
But, to be fair to my response, none of these are an actual argument for the idea that some things exist inexplicably, but simply attacks on sufficient reason.
Take, for instance, his response that sufficient reason is based in the composition fallacy. He argues that you can’t argue that, because all the parts of a thing have a property, that the whole has that property. Every cell in an elephant is light, after all, but the whole elephant is heavy.
But there are two very strong (I would say devastating) responses to this.
The first is the simple fact that this isn’t the main basis on which Leibnitz argues for sufficient reason. It is its status as the basis of inquiry and its a priori obviousness that are the key points.
Still, I’d argue that composition reasoning is valid in addition to this.
If it’s worth pointing out that reasoning from parts to the whole is sometimes wrong-headed, it is also worth pointing out that, at other times, it is entirely appropriate. To throw out another example, if every lego brick used to build a wall is red, then it does indeed follow that the wall is red.
And it seems fairly obvious that the case of the universe is more like the lego wall than the elephant. All the universe is, after all, is a collection of things (space, particles, planets, etc) that need explanations. It is entirely strange to say, then, that the whole collection wouldn’t need one.
Arguing otherwise would be rather like claiming that, though there must be reasons why the links of a chain exist, there is no explanation for the chain itself. This seems obviously false.
At the very least, Mackie owes us an argument. What he does instead is suggest that the universe might be eternal. But, to those who know this argument, this is irrelevant. Leibnitz’s case doesn’t assume the world had a beggining. Even an eternal universe, after all needs to be explained.
Mackie closes his discussion of the argument by claiming that it “fails completely”. But this, more than anything else in his book, struck me as completely wrong. His refutation seemed more a grasping at straws than anything that should shake a theist.
In the end, I find it hard to believe that a non-theist would accept “some things just don’t have explanations” as a defense of theism, and I don’t see any reason why I should accept it as a defense of Mackie’s atheism.