Thomas Aquinas On Original Sin, Part 5.

From Summa Theologica:

Treatise on Habits in Particular, Question 82, Article 1: Whether original sin is a habit?

Aquinas answers that original sin is a habit, with "habit" indicating a disposition toward something. Aquinas argues that due to Adam's sin, mankind suffers a lack of original justice ["justice" being defined in terms of right standing: particularly, in this case, right standing before God] and that from Adam mankind inherits an inclination toward sin. Although Aquinas' theological reasoning in this article seems sound, and I could find some passages- such as Ephesians 2:3- that relate to his assertions, he sadly offers no biblical proof texts in this section.