According to this principle, it is more plausible than not to posit an explanation for some phenomenon if doing so yields gains in terms of explanatory power or prior probability. In combination with other premises, this principle indicates that the existence of all contingent things is best explained by a necessary being whose causal powers raise the probability that contingents things would exist rather than not. Admittedly, this argument did not spell out whether it is reasonable to believe that such a cause is personal or impersonal, but it seems to me that a personal explanation is to be preferred on two counts.
First, if this necessary being was some kind of mechanistic or impersonal cause, then it is difficult to see how there could be contingent things at all – let alone a contingent material universe. Why? Because when the necessary and sufficient conditions for an effect are present, the effect results automatically. There are no delays or mediating constraints. Therefore, if those same casual conditions had existed in every possible world, it follows that the effects would have also existed in every possible world! But since contingent things do exist, the most likely candidate for a cause is a personal one, because a personal being (even one that exists necessarily) can choose to refrain from creating. Its choice (and the reasons it acts upon) explains why contingent things exist because that choice can be made in some worlds and not others.
Second, Occam’s Razor – i.e. the principle that (all other things being equal) we should not multiply causes beyond what is needed – provides a reason to believe that a personal explanation of contingent things is preferable. Why? Because if the contingency argument is used in conjunction with the argument from fundamental order, then it is much simpler to posit one personal explanation for both contingency and order, than to posit two separate explanations: one mechanistic and the other personal.
The two considerations (above) assume that there are only two plausible candidates for the kind of cause involved in the contingency argument: viz. mechanistic or personal. But there may be other types of explanation which are relevant or which we are unaware of. What do you think?
 Of course, this principle of explanation is epistemic and reality need not conform to our epistemic expectations, but such a principle is so basic to the way we explain things in science, philosophy, and (implicitly) in everyday life, that the burden of proof is on the objector to show why the principle does not apply in this case. The success of this principle speaks for itself.