To Dr. Steven Law,
I’ve never seen a cumulative case for God’s existence presented like the one you’ve characterised here. The ones I am familiar with, each argument is without dependency on the other arguments. Less like a single argument being a rung of a ladder to ascend to a height and more like the singular stepping stone necessary to cross a small stream. Multiple arguments individually get you the distance to the opposite bank (the stream being the metaphysical divide between atheist and theism), but each provide different collections of the many attributes of God.
The existence of a necessary being, for example, is proved (purportedly) by all of the cosmological arguments one chooses to use, the design argument, the moral argument, and the ontological argument. The attribute of Goodness, as another example, by the Moral argument, the ontological argument, and the Historical argument for Christ’s resurrection (as it purports to show the God who raised Jesus from the dead is the good God of his revelation to Israel).
Whilst one argument provides attribute A, B, and C, sufficient all on its own to bridge this gap, another argument (a different stepping stone a good distance downstream) provides attributes A, B, and D. The second stepping stone (argument) is for who don’t know about the first, or perhaps find this stepping stone a more preferable or attractive way to cross the stream.
A case for God’s existence only requires one row from the table below, and a successful case will only require one good argument. A cumulative case requires at least two rows from the table below to be argued for. A successful cumulative case will require at least two good arguments, and for one of those good arguments to add at least one attribute of the divine being that is not already added by the previous good argument.
Y = Yes,
N = Not-Attribute
*with supplementary argumentation
**or nearly so
Note that some of the arguments do not show certain attributes, but none show that a certain attribute is inconsistent with the argument. This reveals a third condition for a good cumulative case. A good cumulative case will not show any attribute contradicts another attribute that is shown by another good argument in the case. For instance, the first argument shows A, B and C and the second argument shows A, B and not-C. As an example, if the Kalam Cosmological Argument (is a good argument and) showed that the cause of the universe was not All-good, and the Moral Argument (is also a good argument) showed that the moral law-giver of the universe was All-good, there would be a contradiction between attributes, and it would not be a good cumulative case.
I hope you and your readers found this explanation instructive. All my best.