The question as to whether or not conscience is a reliable guide to ethical decision making can be approached in several ways and often only reaches a personal conclusion fueled by opinion. There are a number of ways in which conscience can be defined, one of which comes from Vincent Macnamara and is considered one of the more modern definitions, it is as follows. Macnamara says the conscience is not a voice but an attitude, he criticised Aquinas for referring to it as a “faculty” we possess. Macnamara regarded life as a moral path and said “it is up to us how we follow it”, furthermore he believes the attitude of our conscience shouldn't revolve around pleasure and profit. His belief is similar, in a way, to the virtue ethics approach and unfortunately boasts the same flaws, where it is hard to determine what is a virtue and what isn't, it's equally difficult to determine whether or not the attitude of our conscience is genuine.

Another theory, put forward by Freud, and later developed by Piaget and Fromm, argues that conscience is more likely a result of environmental factors. This is typical of Freud's beliefs as he was first and foremost a psychologist and scientist with little time for the supernatural or divine. Sigmund Freud's definition of conscience links closely to a human beings feelings of guilt and fear of punishment, this suggests that people may act in order to get approval and could be easily seen as an unreliable guide to ethical decision making. Freud believed that the human mind began to be controlled by powerful desires that must be satisfied as early as birth. Up until the age of 3, these desires are apparently critical to our behaviour and drive the part of the mind Freud refers to as the id. Most people are aware of Freud's theory of the make up of the human mind, he felt there were two categories at war within the id. They would be “eros” (meaning love in ancient Greek, known as the life instinct) and “thanatos” (the name given to Freud's “death drive” by his students). Children apparently are quick to learn that the world puts limits on the extent to which these desires can be fulfilled. In respose to this, the mind creates the “ego” or the “realit principle” which considers the realities of society. The ego provides an awareness of self and others and is crucil to a person's interaction with the wider world. Continuing on from this, the “super-ego”, which develop from the age of 5, reflects the anger and disappointment of others. For this reason it creates a feeling of guilt and this creates the idea of the conscience that Freud is describing. In short, as individuals we are not chooseing to act ethically in order to promote the happiness of others, but to eliminate the feeling of guilt that is generated when we fail to. In this sense, it would seem that Freud's concept of conscience is again not reliable as a guide to ethical decision making, as we don't actually make any decisions ourselves.

There is a very different approach to conscience that exists within the Christian tradition that defines conscience as an innate or intuitive sense, almost like a “sixth sense”. This hails from the early Christian writings of St. Paul. Another proponent of the theory of intuitive sense was Joseph Butler who identified conscience as the ultimate moral decision maker placed in us by God. For this reason the moral decision maker must be listened to and obeyed. However, following this theory it is still possible that the conscience could be misled or misinformed, and for this reason it is still not necessarily a reliable guide.

Aquinas stated that there are two dimensions to moral decision making; synderesis is an awareness of the moral principle to do good and avoid evil and it's counterpart conscientia is the power of reason to work out what is good and evil. The combination of awareness and power to act makes this the most reliable guide to ethical decision-making along with the fact that the theory acknowledges that the genuine human conscience deliberates between the good and bad.

Piaget, an educational psychologist, developed Freud's theory and believed the conscience has the ability to make both mature and immature decisions. The mature part of the conscience is the ego's search for integrity and considers right and wrong. It is aware of the outside world and develops insights into situations. In contrast, according to Piaget there is an immature part that acts out the desire to seek approval from others and doesn't about that persons beliefs or principles. Piaget actually discovered that children up to the age of 10 judge the rightness or wrongness of an action on the consequences, whereas older children link rightness with motive and intention. In this case, the conscience is not innate, but environmentally induced by upbringing. This is another unreliable theory, for the reason that we don't make our decisions based on helping other people or providing happiness, but on our environmental experiences.

Based on all the evidence collected from various psychologists it would seem the conscience is far from a reliable guide to making ethical decisions as the definition of ethical is by default something you do for the benefit of others and not yourself, yet all the evidence points to the conscience being formed and developed by reasons and motives aimed at providing comfort and happiness for ones own mind. However, based on personal experience, I would conclude that the conscience is the only means by which to make an ethical decision, for this is the part of the human mind that makes one feel empathy and compassion and these things are what urge people to act on when it comes to making ethical decisions. Although the conscience may be formed by a slight need to make oneself feel better and may be a result of personal upbringing it is inevitably this entity that we can thank for the decisions made that make the world a more ethically rich place.