In the field of moral conduct there are similar first principles of action, such as: "evil must be avoided, good done"; "Do not do to others what you would not wish to be done to yourself"; "Parents should be honoured"; "We should live temperately and act justly".
Such as these are self-evident truths in the field of moral conduct which any sane person will admit if he understands them.
According to the Scholastics, the readiness with which such moral truths are apprehended by the practical intellect is due to the natural habit impressed on the cognitive faculty which they call synderesis.
[1] The notion of synderesis has a long tradition, including the Commentary on Ezekiel by Jerome (A.D. 347–419), where syntéresin (συντήρησιν) is mentioned among the powers of the soul and is described as the spark of conscience (scintilla conscientiae),[2] and the interpretation of Jerome's text given, in the 13th century, by Albert the Great and Thomas Aquinas in the light of Aristotelian psychology and ethics.
An alternative interpretation of synderesis was proposed by Bonaventure, who considered it as the natural inclination of the will towards moral good.