A traditional staple of cosmological arguments is that at some point after one has established that there is a First Cause, one applies the Reality Principle (RP): If C is the cause of E, then C has at least the reality of the effect. If true, the RP is very helpful. Since among the things caused are intelligent beings, we immediately conclude that the First Cause has at least intelligence, i.e., has intelligence or some attribute greater than intelligence. This helps with the Gap Problem—the problem of showing that the First Cause is appropriately identified as God.
Aquinas, Descartes and Clarke all use a version of the RP in at least one of their respective arguments. Aquinas and Descartes, as far as I know, give no argument. Clarke gives arguments (see p. 49ff), but they are not very plausible to those not already persuaded. The basic intuition behind the RP is either that one cannot give what one does not have (Clarke, ibid.) or that the cause must be relevantly like the effect (Freddoso, email communication). I think there is something to the intuition but don't at present have a better argument.
Note that the RP would make emergentism quite implausible. So figuring out whether the RP is true would advance the discussion in areas other than natural theology.
