Calvinism "...fails to distinguish the classical doctrine from a Molinist doctrine, according to which believers can fall away but in fact will not due to God's extrinsically efficacious grace...does not clearly distinguish the classical doctrine of perseverance from a Molinist version."

"Any believer who has been warned by God cannot fall away is...true in sensu composito, that is to say, it is true that Necessarily, a believer who has been warned by God will not fall away."

"According to Molina, divine grace is extrinsically efficacious, that is to say, it becomes efficacious when conjoined with the free co-operation of the creaturely will. On Molina's view, God gives sufficient grace for salvation to all men, but it becomes efficacious [once-saved-always-saved] only in the lives of those who respond affirmatively to it." The point here is that grace is eternally efficacious for those who believe by faith so they can never fall away.

"Not really perseverance, but preservation that is at issue here" says Craig for preservation of the saints is OSAS Arminian/Molinism. We distinguish between a person able to fall away but never does, because nothing convinces him otherwise by God's wonderfully supplied grace for those who make an authentic choice for Him.

"God's grace is...extrinsically efficacious.... It is broadly logically impossible that he fall away."

"A maximally perfect being would not create a situation of such unremittingsuffering [where you could lose eternal life after receiving it at new birth]...because God in His essential goodness always acts so as to win the free, affirmative response of believers to His grace.... God is too good to fail to provide additional gifts of grace.... grace which is so suited to the created will that were it to be offered, it would not be rejected."

"The integrity of God's goodness and faithfulness to the believer is retained in such worlds because He offers the believer the greatest gracious help that He can...there is no realizable world in which believers fall away and are lost.... God is no doubt pleased that worlds in which believers fall away are infeasible for Him."

"In the world He chose to actualize, believers always persevere in the faith. It is therefore clear that while all truly regenerate believers will persevere to the end, nevertheless they are free to fall away."

"In the moment logically prior to creation, God via His middle knowledge knew who would freely receive Christ as Savior and what sorts of warnings against apostasy would be extrinsically efficacious in keeping them from falling away. Therefore, He decreed to create only those persons to be saved who He knew would freely respond to His warnings and thus persevere, and He simultaneously decreed to provide such warnings. On this account the believer will certainly persevere and yet he does so freely, taking seriously the warnings God has given him." Warnings would be for the purpose of rewards and loss of rewards for the millennial reign with Christ.

Also see:
http://www.ericknelson.net/Apol/Know...%20Showing.htm
http://biblocality.com/forums/showthread.php?t=2750 (popular Molinism articles by Craig)