Give me scripture on that thought so I can make a better response to your statement.
I can't answer for Jonathan, but the scriptures show the natural man can be enlightened, and even brought to the point of repentance and still fall away in unbelief.
Heb 6:4 For
it is impossible for those who were once
enlightened, and have
tasted of the heavenly gift, and were made
partakers of the Holy Ghost,
5 And have
tasted the good word of God, and the powers of the world to come,
6 If they shall fall away,
to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put
him to an open shame.
7 For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God:
8 But that which beareth thorns and briers
is rejected, and
is nigh unto cursing; whose end
is to be burned.
9 But, beloved, we are persuaded better things of you, and things that accompany salvation, though we thus speak.
Now, I tend to agree with Willis, it is not the flesh or natural man that is enlightened, but the spirit of man. But these scriptures show a man can be enlightened or taught, that is, brought to an understanding of what they need to do to be saved, and yet fall away in unbelief. They can be brought to the point of repentance, and yet turn away. They can "taste" of salvation, but do not "eat".
They are compared to earth that God has graciously rained upon and dressed, but instead of bringing forth herbs which God intended, bring forth thorns and briers.
This is not speaking of believers, otherwise you must believe that a person can lose their salvation. No, this is speaking of natural men who are brought to understanding and repentance by God, but who turn away in unbelief. There is no more solution for them. I believe from this point on these persons will be progressively hardened to the gospel, a very dangerous place to be.