The Consequences Of Refusing To Have God In Their Knowledge (1:28-32).
Paul now moves on from the results of ungodliness to the results of unrighteousness (compare Romans 1:18). Men refused to have God in their knowledge. They ‘did not want to know' because they did not want to submit to His demands. As a consequence God gave them up to an unfit mind so that they would do those things which were not fitting. In Romans 1:24 He had given them up to the lust of their hearts. Now He gives them up to a reprobate (rejected after testing, unfit, spurious) mind. There is a clear intention of bringing out that God is active in punishing ungodliness and unrighteousness by disposing men and women to greater ungodliness and unrighteousness, so that in the end some at least will get sick of it.
This will be confirmed by what follows, a long list of the sins that reveal the bestiality of men's minds. Regularly in Scripture the natural man is likened to a wild beast, while in contrast those who keep God's covenant are described in terms of ‘a son of man' (see for this especially Daniel 7). Here man's beastliness is seen as coming out. It is only the man who obeys God, who retains the true image of God. It will be noted that no sexual sins are listed in Romans 1:28-31, those having already been dealt with in Romans 1:24-27 as especially heinous, because they replace the true worship of God. What follows are the kind of sins common to mankind, and they cover all aspects of human behaviour leaving none of us untouched. The point that Paul is bringing out is that without exception all have sinned in one way or another.