Luther and the Calvinists went overboard by denying the existence of free will as well as the existence of the conscience, and postulating that the unsaved are unremittingly evil. They were simply following the Catholic St Augustine.
Something else which is totally ignored so as to persist in this false doctrine is what John said about Christ:
In him was life; and the life was the light of men... That was the true Light, which lighteth every man that cometh into the world. (John 1:4,9).
This is God, telling us through John, that every human being receives a measure of the light of Christ when he or she is born. So in what sense do humans have light? Paul explains this is Romans 2.
7 To them who by patient continuance in well doing seek for glory and honour and immortality, eternal life:
8 But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath,
9 Tribulation and anguish, upon every soul of man that doeth evil, of the Jew first, and also of the Gentile;
10 But glory, honour, and peace, to every man that worketh good, to the Jew first, and also to the Gentile:
11 For there is no respect of persons with God.
12 For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law;
13 For not the hearers of the law are just before God, but the doers of the law shall be justified.
14 For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves:
15 Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another,
16 In the day when God shall judge the secrets of men by Jesus Christ according to my gospel.
What is "the law written in their hearts"? Is it not the Ten Commandments, which work through the conscience, so that even unsaved Gentiles can discern right from wrong, and do what is right?
Furthermore God has revealed Himself in His creation, which leaves all men without excuse: Because that which may be known of God is manifest in them; for God hath shewed it unto them. For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: (Rom 1:19,20)