(3) From a Possible Beginning to the Possibility of Necessary Exis-tence: if (1) and (2) are true, then it is possible that there is a necessary concrete thing.
(4) Therefore, it is possible that there is a necessary concrete thing.
How good is Necessitarian Response to FTA?
Ben Page while Discussing This response notes that
"the necessitarian response, put simply, says the laws and constants of nature are metaphysically necessary, such that they do not vary across possible worlds.
In the end as Ben page himself concludes
"If given in terms of inference to the best explanation I claim the response can be
potent. Yet when given to a Bayesian formulation of the argument the response seems impotent"
As Ben page notes that indeed it is metaphysically necessary That clark kent is superman, But the epistemic justification to believe in it doesn't hangs upon the necessity of it. (For more detailed discussion Check, Hawthorne)
In Contemporary Natural theology some of the best arguments for god Revolves around W PSR and W-CP, Both of these principles have been extensively used by Alex Pruss and Joshua Rasmussen, Though it is argued That both of these principles are no better than strong ones
(We aren't saying that every philosopher agree with grounding as explanation, The thing is this is a well documented position that is held by many philosophers)