Gottfried Wilhelm Leibniz was a 17th century German philosopher and mathematician, and he is responsible for the next argument for God's existence that we will deal with.
Leibniz was crazy. Crazy smart. But also just crazy. (That's him sportin' the awesome wig to the right...)
Many do not realize that he independently discovered infinitesimal calculus around the same time as Isaac Newton. Yep. He just figured it out. In fact, he and Newton had a notoriously rocky relationship, each accusing the other of plagiarism. Unfortunately for Leibniz, Newton apparently had a few more influential friends, and so aside from a few mathematical notations, Leibniz is remembered these days mostly for his philosophical work.
Fortunately for us, Leibniz' argument for the existence of God can stand independently from the rest of his philosophy. This is good because it isn't clear whether anyone in the world really fully understands his philosophy. Like I said, crazy.
So without further ado, the argument:
(1) Anything that exists has an explanation of its existence, either in its own nature or in an external cause.
(2) If the universe has an explanation of its existence, then that explanation is God.
(3) The universe exists.
(4) The universe has an explanation of its existence. (From 1 & 3)
(5) The explanation of the existence of the universe is God. (From 2 & 4)
This argument differs from the Kalam is a couple significant ways. First, it does not rely on causal relations, but rather explanatory ones. And second, it does not need the impossibility of an infinite series of events to make its case. In other words, it would work just as well even if the universe were eternal. This makes sense, since in Leibniz' day we didn't have the compelling cosmological evidence for the beginning of the universe that we discussed in the last post.
For the fans of logic out there, it is clear that the argument is valid (for the others, that just means there's no mistake in how it is formulated). The question then is whether the premises are true. Hopefully, no one reading this doubts premise (3). The first two are a bit more controversial though.
I have already dealt with (2) in a previous post. As I showed there, once we consider what it really means to be the cause of the universe, it is not much of a jump to the theistic God. The same holds for an explanation of the existence of the universe (see especially the second argument I offered for a personal cause in that post).
I do want to point out one more interesting thing about (2): it is logically equivalent to a common atheistic response to the Leibnizian argument. When two statements are logically equivalent, it means that if one is true, so is the other, and vice versa. A popular response is that if atheism is true, then the universe doesn't have an explanation for its existence; it just exists. But in affirming this, the objector is also affirming the opposite of this claim, which is just premise (2). Thus, it seems that even the atheist tends to think that (2) is intuitively obvious. I wonder how many of them realize this...
What about premise (1)? This one, too, seems obvious to most honest people, regardless of their beliefs about God. It's rather difficult to imagine something existing totally inexplicably and our being okay with it. William Lane Craig offers a good illustration of this: Imagine that you and a friend are hiking in the forest when you come across a large translucent ball lying on the ground. You ask why it is there, and your friend simply replies, "What do you mean why is it there? There is no explanation. It's just there." Would you be satisfied with this answer? Of course not. And to make the analogy more interesting, the size of the ball has no affect whatsoever on the inadequacy of the response. We can imagine it being any size--even as large as the universe itself--and its existence still requires an explanation.
Premise (1) is a form of what has come to be called, since Leibniz, the Principle of Sufficient Reason (PSR). There have been whole books devoted to this principle (I know; I read one about a year ago). The discussions involved are very dense and technical, so I won't go into too much detail here. I will say that in the end though, I think that everyone's initial intuition about PSR is probably right.
I'll give some reasons for this and discuss a few of the major objections to the principle in the next post.