Oh, trust me, Finney did not believe once saved always saved. Read up on him if you need to confirm that. In 1610, when the follower of Jacob Arminius put together the The Five Articles of the Remonstrants (to which the five points of Calvinism TULIP was later a response) the fifth point had this to say...
Article 5.
[Assurance and Security - corresponds to the fifth of TULIP’s five points, Perseverance of the Saints]
That those who are incorporated into Christ by true faith, and have thereby become partakers of his life-giving Spirit, as a result have full power to strive against Satan, sin, the world, and their own flesh, and to win the victory; it being well understood that it is ever through the assisting grace of the Holy Spirit; and that Jesus Christ assists them through his Spirit in all temptations, extends to them his hand, and if only they are ready for the conflict, desire his help, and are not inactive, keeps them from falling, so that they, by no deceit or power of Satan, can be misled nor plucked out of Christ’s hands, according to the Word of Christ, John 10:28: “Neither shall any man pluck them out of my hand.” But whether they are capable, through negligence, of forsaking again the first beginning of their life in Christ, of again returning to this present evil world, of turning away from the holy doctrine which was delivered them, of losing a good conscience, of neglecting grace, that must be more particularly determined out of the Holy Scripture, before we ourselves can teach it with the full confidence of our mind.
These Articles, thus set forth and taught, the Remonstrants deem agreeable to the Word of God, tending to edification, and, as regards this argument, sufficient for salvation, so that it is not necessary or edifying to rise higher or to descend deeper.
The Articles of the Remonstrants are adapted from Phillip Schaff, The Creeds of Christendom, Volume 3, Baker Books, Grand Rapids, 1996, pp 545ff.
Now while they did not state (at this time) with any certainty that salvation could be lost, they did leave open the possibility. Arminius, himself, said that
"I never taught that a true believer can… fall away from the faith… yet I will not conceal, that there are passages of Scripture which seem to me to wear this aspect; and those answers to them which I have been permitted to see, are not of such as kind as to approve themselves on all points to my understanding."
John Wesley is really the one who picked up the ball and more fully developed Arminianism as we have it today and his view of the issue was as follows.... Wesley fully accepted the Arminian view that genuine Christians could apostatize and lose their salvation, as his famous sermon "A Call to Backsliders" clearly demonstrates. Harper summarizes as follows: "the act of committing sin is not in itself ground for the loss of salvation...the loss of salvation is much more related to experiences that are profound and prolonged. Wesley sees two primary pathways that could result in a permanent fall from grace: unconfessed sin and the actual expression of apostasy." Wesley disagrees with Arminius, however, in maintaining that such apostasy was not final. When talking about those who have made "shipwreck" of their faith (1 Tim 1:19), Wesley claims that "not one, or a hundred only, but I am persuaded, several thousands...innumerable are the instances...of those who had fallen but now stand upright."
So you see, so serious was it to the Calvinists that Arminius left open even the possibility that one could fall from grace, that they responded with their doctrine, The Perseverance of the Saints. Every significant Arminian theologian that I know of has believed and taught at least the possibility that the true believer can become apostate.
