What possible reasons might Abraham Lincoln have had for wanting to put himself to some inconvenience to rescue piglets from a slough? The simplest reason might be to spare himself from the annoying, unpleasant sounds of the squealing piglets and their mother. In the same way, a restaurant customer who finds a squalling baby at the next table might ask to be seated somewhere else. This would be at once a natural and a narrowly self-interested motivation -- the restaurant customer who finds the baby's cries unpleasant isn't doing to alleviate the baby's presumed distress, only getting away from it.. However, Lincoln was in a moving coach. He was not going to be subjected to the piglets' squealings until they drowned; he could have done nothing, and they would have been out of earshot in a minute or two, even at stagecoach speeds.
A second reason Lincoln might have rescued the piglets was to bask in the esteem of his fellow passengers. Most people enjoy being admired. Since Lincoln was a politician, he perhaps enjoyed being admired even more than most people do. Admiration can translate into votes, while a strong desire for admiration can be a motive to go into elective politics in the first place. To be sure, Lincoln denies that he rescued the piglets it for an admirable reason, asserting that his own action was purely selfish. This, however, might simply be a pose, assuming the expected modesty of a proper hero.
However, let us take Lincoln at his word. He says he did it for his own peace of mind. He is implicitly asserting that he felt empathy for the piglets, or at any rate for their mother, the sow. The sound of the piglets' squeals could be left behind, but not the knowledge of their suffering and the sow's struggles to save them. We may note in passing that this claim might itself be a ploy to win his his fellow-passengers' admiration. However, let us again suppose that Honest Abe was telling the truth, an...