Problem: David claimed that he was “conceived” in sin in his mother’s womb. However, he could not have actually sinned at the moment of conception, since he had no moral consciousness or free will which are necessary for moral acts (see Isa. 7:15; John 9:41).
Solution: This text does not support the view that a human embryo is merely a potential human being, as opposed to an actual human being. This is evident for several reasons. First, even if it were teaching that humans are potential sinners from conception, it does not follow that they are potential humans.
Second, in whatever sense the unborn are declared sinners from the point of conception, it reveals, nevertheless, that they are human, that is, they are part of the fallen human race. For it is only by virtue of being part of the Adamic human race that we are conceived in sin (see comments on Rom. 5:12).
