(Please comment and critique. This is poorly and quickly written and I haven't thought through my defense of it at all yet. This is only a sketch of a theory, not a discussion yet; to fully assert this, I need to engage with opposing views, so long as they remain within the boundaries of my premises.)
Abstract: I argue that sinlessness can never be achieved by a human will, for the epistemic reason that our willing, even if both efficacious and capable of independent action, will never have a complete knowledge of our sin upon which to act.
A system of thought into which it is common to fall is that of the Pelagians: specifically, their belief that we are responsible, once our sinful condition is brought to light, for our own salvation and the accompanying purge of sinful actions from our character and nature. This proposition is commonly thought to be a heresy, and I intend here to provide an epistemological argument affirming this view of it. I have never come across this argument before, but that does not necessarily make it novel; regardless, I will either be presenting a new argument or re-presenting a classical argument in new language.
I take as premises an absolutely sinful nature, "sinful" defined as "diverging from God's will" (whether inherited as "original sin" or come-into as an "adopted maxim"), man as a willing and willful agent, the limited nature of man, and the infinite nature of God.
The intransigent nature of man is as a sinful creature, whether metaphysically inherited in our common substance or chosen willfully at some time during youth (see Psalm 51:5). The opposite is experientially untenable: I know of no one who would claim that, under the standards given in Scripture (see Matthew 5), they are or have ever come across an individual above the age of accountability who is sinless. Regardless, it is highly attractive - if not even intuitive - to assert* what I will call a "quasi-Pelagian" doctrine of salvation: that, when the reality of sinfulness is revealed to us, and, opposed to it, a Godly moral code outlined, it is possible for me to, under my own willing and through my own actions, reject that sinfulness and adopt that moral code, thereby removing the grounds for condemnation from myself and achieving some sort of standard of good living that restores me to my original condition, as I would have been pre-fall.
I disagree with "quasi-Pelagian" salvation, attractive though it may seem. This view essentially asserts two propositions: one of volition (i.e., "I can actually desire not to be sinful") and one of knowledge (i.e., "I can actually know my sinful condition"). Many arguments against this view reject it from the implausibility of volition and efficacity: that is, it is impossible for me, unaided, to actually will against committing sin (supported by Romans 7:15-16). And, even if I can desire not to sin, that desire fails to be efficacious: it fails to actually motivate me to reject sin.
However, I think that another argument can be raised against "quasi-Pelagian" salvation, grounded in the implausibility of knowledge: I find epistemic grounds for our continued existence in a sinful condition, even granting a volition to exist in a sinless condition. My reasoning is as such:
3) Man is absolutely sinful**, and not omniscient.
5) Salvation requires a return to a fully sinless state.
6) (from 4 and 5) Man is unable to effect his own salvation.
In (2), I claim that God is absolutely good (which obtains, from the definition of "good" as "adhering to the will of God") and omniscient (as a premise). In (3), I claim that man is absolutely sinful and not omniscient (both premises). Because our sin is absolute, it is an absolute truth, so, (3b).
(4) follows from the definition of an absolute truth (Def.1), that man is not omniscient (3), and that our sin is an absolute truth (3b).
(5) is a claim that salvation is constituted by a restoration of the will to full concordance with God's own. I think that this is a relatively uncontroversial claim.
Finally, (6) follows from (4) and (5): since we do not know our sin fully (4), we cannot know how to reject it in full and, at best, reject it in part, which fails to satisfy (5), the criteria for salvation.
To illustrate, it may help to separate actions into four categories, along two axes: known-unknown and moral-immoral. As such, there are four kinds of actions: knowingly moral, unknowingly moral, knowingly immoral, and unknowingly immoral. As any good Calvinist would immediately say in response, we can deny the possibility of there actually existing moral actions, due to the taint of sin in our motivations. But this is not even necessary for my argument: let's imagine, for the time being, that moral actions can exist. Still, there remain the two sorts of immoral actions condemning us. Even if our will is independent and efficacious (that is, that we can actually independently will ourselves to adopt a maxim of action, and then do so), then willing to reject sinful actions only gets rid of knowingly sinful actions. There still remain those cases of unknowing sin to condemn us. Humanity, before the fall (whether a personal fall or a prehistorical fall), was in compliance in toto with the will of God, even unconsciously and uncomprehendingly (i.e. in the absolute sense). After the fall, the best possible state we can hope to achieve under our own power is less than this: we can comply with the will of God only so far as we are cognizant of it, in a human and limited, and not absolute, sense.
This is why I term sin "recalcitrant": regardless of how thoroughly an individual rejects his sin, his will still remains sinful. Self-perfection only permeates through the set of human truths; it fails to motivate (because it cannot) an alteration of one's actions motivated by the adoption of absolute truths. This is why "quasi-Pelagian" views of salvation fail to satisfy the criteria for salvation: they restore our will only partly to that of God. We still remain in unconscious and uncomprehending divergence from his will, simply because we cannot know the true richness and depth of that Godly will. The only agent that can possibly act to restore us in whole to the will of God is an agent that has two qualities: (1) transformative power in our own lives, and (2) thorough comprehension of the will and character of God.
*And, I think, even if we do not adopt this view in our theology, it can be tempting, in our weaker moments of self-confidence, to fall prey to such denials of our deep depravity.
**By "absolutely sinful", I mean, "sinful on every level of understanding," and that requires arguing that our adoption of a sinful maxim corrupts us on every level of understanding, even those to which our intellects are insensitive.