"It is most certain that there are two estates and conditions that divide all mankind, and every one that lives in the world doth completely and absolutely belong unto one of them. These are, the state of nature and the state of grace, - of sin and of righteousness by Christ. Every man in the world belongs unto one of these states or conditions...But here also observe, - That I do not say that is always known to the persons themselves...either think[ing] themselves regenerate when they are not, or...many that are truly born of God yet know it not...Nor, - That this is always known to others. It is not known unto unregenerate men...Nor is this always known unto or discerned by them that are regenerate...The judgement of man may fail...[Nevertheless]...It may be known...and that infallibly and assuredly...".
-John Owen, "An Exposition of Psalm 130". The Works of John Owen, Volume VI. The Banner of Truth Trust: Carlisle, PA. (1668) 2000. pp.584, 588-589.