The Principle of Sufficient Reason, Clarke's Version
Clarke's Second Reply
Clarke: "It is very true that nothing is without a sufficient reason why it is, and why it is thus rather than otherwise. ... But this sufficient reason is often times no other than the mere will of God. There can be no other reason but the mere will of God, for instance, why this particular system of matter should be created in one particular place, and ..."
Does this look reasonable? If you think merely in terms of "God's will", you may think this may be right. But wait a minute! Raise similar questions in terms of scientific matters, the big bang cosmology, for instance. Then Clarke's reply seems to be a mere verbal evasion. Here is a good example:
A common misconception is that the big bang provides a theory of cosmic origins. It doesn't. The big bang is a theory ... that delineates cosmic evolution from a split second after whatever happened to bring the universe into existence, but it says nothing at all about the time zero itself. And since ... the bang is what is supposed to have happened at the beginning, the big bang leaves out the bang. It tells us nothing about what banged, why it banged, how it banged, or, frankly, whether it ever really banged at all. In fact, if you think about it for a moment, you'll realize that the big bang presents us with quite a puzzle. (Greene 2004, 272)
Can you see the thrust of this passage? Borrowing Clarke's terminology, the big bang theory is saying merely that "when, how, and why the big bang occurred, that's the mere will of God". Many cosmologists want to know the "reason" for this "will of God", and this is how Leibniz's principle of sufficient reason works.
To be fair to the Newtonians, however, it must be noted that Newton's view may well come from his considerations of cosmology. Newton, in his correspondence (around 1692) with Richard Bentley (1662-1742) expressed the view that the universe must be infinite and all matter is uniformly distributed in it (otherwise, because of the universal attractive gravity, the matter, finite in amount, will be concentrated at the center of the universe; and this is apparently against our experience) . The problem with this infinite uniform universe is that it is not stable; any slight disturbance may destroy the equilibrium. Then why does the actual universe look so stable? There must be some cause responsible for that, and that may well be God's continual intervention (see ハリソン2004, 106-110).
However, there still remain several questions. Did Clarke know Newton's view of the infinite and with the matter uniformly distributed universe? If he knew, then why did not he make use of that knowledge? For, since such a universe has an infinite amount of matter, Clarke should have answered Leibniz's objection straightforwardly, by saying that God created an infinite amount of matter, despite empty space in between; there should be no point in saying "more matter or less matter".
References
Greene, Brian (2004) The Fabric of the Cosmos, Allen Lane.
ハリソン、E. (2004) 『夜空はなぜ暗い？』（長沢工監訳）地人書館（原著1987）
Last modified, May 11, 2005. (c) Soshichi Uchii