[Vigilanteman]

You are also correct. But admitting the existence of a conscience would tend to support those who argue that children are born with an innate nature to do good and thus weaken the argument that children are born with a sinful nature.

Since the prevailing theology of the time (and even our time) is that children are born with a sinful nature, I think it entirely possible that Lincoln was taking the opposite side, but if so, I can't see the preacher arguing that Lincoln's decision to save the piglets was motivated from an evil nature.

The story, I think, is much like the C.S. Lewis conundrum cited in the post.

[TalonDJ]

But admitting the existence of a conscience would tend to support those who argue that children are born with an innate nature to do good and thus weaken the argument that children are born with a sinful nature.

Not at all. The Bible is very clear that we are born with both. The sin nature does not mean we fail to recognize good. Our conscience shows of the moral path from a very early age. Our sin nature means we are incapable of following the moral path all of the time. Of course even the definition and extent of 'sin nature' varies between various denominations. But sin nature in no way is contradictory with an inborn conscience.