The Conscience and Aquinas
In Summa Theologica, Aquinas outlines his views on the conscience. Aquinas states that the conscience is a God-given faculty from which we can effectively differentiate between 'good' and 'bad'. Aquinas believed that in order to do this properly, we must first understand that there are two aspects of the conscience; the synderesis and the conscientia.
By synderesis, Aquinas believed that this was a collection of moral principles that are ascertained through an observation of the Natural Law of God, a necessary deduction using our reason from which we can understand the divine primary precepts. To Aquinas, the most important background to the divine Natural Law was the idea that ''good must be pursued and evil to be avoided''. If this was not fully enshrined in our conscience then we risk pursuing 'apparent goods'.
Aquinas states that 'apparent goods' come about because of a flawed synderisis. The error that is made with an apparent good is a vincible error- an error made knowingly. For instance, if the primary precept of eudaimonia is not understood and the conscience of a man tells him to cheat on his wife in secret (apparent good) but knows that he'll upset his marital relationship then his conscience is flawed as he fails to understand the immorality behind ''cheating''.Therefore, one must first establish a completed synderisis before the conscience can be moral as well. A completeld synderisis is therefore,…