(or synteresis )
The supposed natural or innate ability of the mind to know the first principles of ethics and moral reasoning. Although traced to Aristotle, the phrase came to the modern era through St Jerome, whose scintilla conscientiae (gleam of conscience) was a popular concept in early scholasticism. But it is mainly associated with Aquinas, as an infallible, natural, simple, and immediate grasp of first moral principles. Conscience, by contrast, is more concerned with particular instances of right and wrong, and can be in error.
Philosophy dictionary. Academic. 2011.