Aquinas believes that conscience is the process of reasoning: our rational ability to understand the
difference between right and wrong.
He believes that the ability to reason ‘ratio’ is placed in every human due to being created in the
image of God. It then becomes our responsibility use ‘ratio’ correctly. We do this by developing the
intellectual virtue of prudence or phronesis – our ability to make reasoned judgements based on the
circumstances we find ourselves in. By using our moral conscience, we develop it.
For Aquinas, conscience comes in two parts – synderesis and conscientia.
Synderesis is our natural inclination to ‘do good and avoid evil.’ It is a habit of reasoning that we
develop with practice so that we will come to understand and be able to apply moral rules.
Conscientia is the practical outworking of synderesis: the intellectual process of making moral
judgements and applying them to the situations we are in. Again, this is a skill that should be
practiced and developed.
Conscience is basically our ability to use natural law. Synderesis is the key and primary precepts and
conscientia is our faculty of reason.
In other theological views where God speaks to us or gives an infallible intuition, it is difficult to see
how conscience could be mistaken. Aquinas is optimistic about human nature and believes we do
not deliberately choose evil acts but rather mistakenly pursue apparent goods. As such, all wrong
actions, and the errors of conscience, stem from ignorance.
Vincible ignorance involves a lack of knowledge for which the person is responsible e.g if a man
commits adultery because he is unaware of the moral rule against it or believes it does not apply in
his case.
Invincible ignorance involves a lack of knowledge for which the person is not responsible and could
not possibly have known their action was wrong e.g if a man knowing adultery was wrong slept with
a women believing her to be his wife then there is no wrongdoing.
AO2: This view, by emphasising individual reasoning in conscience, provides an explanation of why
conscience can be wrong and moral disagreement. If conscience were directly linked to God – as
Augustine or Newman believe - then it is hard to see why people would disagree over right and
wrong.
AO2: In the Bible Paul explains that God’s laws are ‘written in our hearts.’ He also warns that people
can sear or damage their conscience by persistently not listening to it. This supports Aquinas’ view
that conscience is a habit to be developed and nurtured.
AO2: Based around knowledge and reasoning so that every religion can apply it.
AO2: The epistemology of conscience comes from conscientia which means reasoned decision
making
AO2: This view does not fit with how we experience conscience. We are conscious of a more
immediate and intuitive sense of right or wrong rather than a process of deliberation and reflection.