Søren Kierkegaard was a Christian author who was against applying the ideas of the Scientific Enlightenment to Christianity. He lived in Denmark from 1813 to 1855. His works were written to the single individual who might be interested in reading them.
Soren wasn’t so afraid of sin as he was of the consequences for any individual, like his own father, who at 82 years old couldn’t forget what he had done 70 years earlier, and couldn’t believe he could be forgiven. As far as Regine goes he had good reasons to break off his engagement and explained them in his book Prefaces.