For if God’s causal activity is necessary, then God’s causing this universe is necessary, and hence this universe is a necessary being, which is absurd, besides being contrary to the assumptions of typical cosmological arguments. But this objection commits a de re/de dicto fallacy. Consider the argument written out:
- C1 is God’s causal activity and is a necessary being. (Premise)
- C1 is God’s causing E. (Premise)
- Therefore, God’s causing E is a necessary being.
- Therefore, God necessarily causes E.
- The F is a necessary being
- Therefore, necessarily, F exists.
The fallacy is in the last steps 5 and 6.
But this is fallacious if “the F” in (6) is read de dicto, as it must be in the case where F is “God’s causing E.” The number of eyes of the tallest person is, let us suppose, the number two and, let us also suppose, that the number two is a necessary Platonic being. But it is incorrect to conclude that, necessarily, the number of eyes of the tallest person exists, since that would entail the falsehood that necessarily there is a tallest person (it could be that no person has a height or that there is a tie).
The inference from (5) to (6) requires that Fness be an essential property of the F. It is not an essential property of the number two that it is the number of eyes of the tallest person, and hence the inference fails in that case. Similarly, in the God case, the argument is only going to work if it is an essential property of God’s activity that it be the same as God’s causing E. But these proponents of divine simplicity should deny. They should instead insist that the same activity would count as God’s causing E in those worlds where God causes E and as God’s causing F in those worlds where God causes F. A very imperfect analogy for this is that the same act of writing down a sequence of numbers is, in some worlds, the ﬁlling out of a winning lottery ticket and in others the ﬁlling out of a losing lottery ticket. The reason for the imperfection in the example is that in the lottery case, it does not depend on the act, which lottery tickets are drawn, but everything, in some way, depends on God’s act. But it should be no surprise if there is no close analogue to doctrines coming from divine simplicity. 
 Alexander Pruss, “The Leibnizian Cosmological Argument,” in The Blackwell Companion to Natural Theology Eds. William Lane Craig and J.P. Moreland (Oxford, UK: Blackwell, 2009), 76-77.