Santiago's research focuses on ancient ethics and ancient economic thought. Within these areas, he studies the relationship between self-interest and other-regarding behaviour, the link between material prosperity and happiness, and the role of the emotions in moral development. Santiago is also interested in exploring the influence of ancient Greek and Roman philosophy on early Christian thought, particularly on the attempted solutions to the problem of evil. Since 2014, Santiago has been consulting editor for the Richard Rufus of Cornwall Project led by Prof. Rega Wood, working mainly on the translation of Rufus' Scriptum in Metaphysicam Aristotelis. He graduated from Stanford University with an M.A. in Ancient Philosophy in 2016.