Eternal sin
Thomas Aquinas lists, or has responded to, six sins that supposedly go against the Holy Spirit:
Thomas Aquinas explains that the unforgivability of blasphemy against the Holy Spirit means that it removes the entrance to these means of salvation; however, it cannot hinder God in taking away this obstacle by way of a miracle.
Christian views on sin
Original sin, also called ancestral sin, is the Christian doctrine of humanity's state of sin resulting from the fall of man, stemming from Adam's rebellion in Eden, namely the sin of disobedience in consuming from the tree of knowledge of good and evil. This condition has been characterized in many ways, ranging from something as insignificant as a slight deficiency, or a tendency toward sin yet without collective guilt, referred to as a "sin nature", to something as drastic as total depravity or automatic guilt of all humans through collective guilt.