The Character of God as Guarantee of the Saint's Perseverance

"It is impossible [that] we should lose the thing we were wrought for, because it is God that wrought it for us. It is not the designment of an idol; that is, of some ignorant, rash, fallible, or mutable agent, such a one as may possibly be surprised by unlooked-for accidents, circumvented by a sublimer understanding, overborne by a power above him, or recede from his purpose through levity and fickleness of his nature, etc. But it is God who is 'wise in heart and mighty in strength,' Job 9:4. It is He from whom all things that are have their being and are perfectly under His rule and obeisance. He had eternity before Him, to lay His design surely; and, accordingly, 'He declared the end from the beginning.' It is, therefore, as impossible for Him either to do or to neglect to do, or to suffer to be done, anything whereby His purpose might suffer disappointment, as it is impossible that God should lie. He would never have set up those ends as the sum and substance of His design, if He had not determined to see them made good." -Puritan Elisha Coles, "A Practical Discourse of God's Sovereignty 

Part of the Creator/creature distinction is that the Creator is omniscient, omnipotent, and eternal, while the creature has all but three of those attributes. A creaturely awareness is conscious of our inability to plan for all contingencies, at all times, as may disrupt our best-laid plans. For example, the farmer cannot know of the coming hurricane that wipes out his crop. In contrast, the triune God of the Bible has infinite awareness across all time, all space, and under all contingencies, such that His plans are infallibly achieved. As in the verse that Coles quotes, "I am God, and there is none like Me, declaring the end from the beginning and from ancient times things not yet done, saying, 'My counsel shall stand, and I will accomplish My purpose'" (Isaiah 46:10). It would be comical hubris for any human to make such an assertion. 

However, it is also unforgiveable hubris to assert such infallibility for any man's ability to keep himself in a state of grace. Yet that is what the Arminian does, when he claims that no man can keep himself saved, and, therefore, he should never be assured of his hold on eternal life. If the fundamental assumption of the Arminian, that it is the will of the man that should thus preserve him, then it would be true that no man could ever know an assurance of salvation in this life. 

But this is exactly what perseverance is not. It does not, has never, and never shall, depend on the will and power of the creature to maintain his state of grace. It is the work of God alone, He whose irrepeatable attributes of deity guarantee that any man, truly saved, can never fully and finally lose his salvation. Thus, his assurance is sound, not because of any ability of his own, but because of the infallible character of the God who saved him to begin with.