Moral Realism

Plato believed in order to lead a life worth living one must know and understand the Form of the Good. The essential nature of goodness is the universal and significant feature of all good acts. When one knows the Form of the Good one may then asses whether moral acts conform to this truth. Similarly to mathematics, in that we can determine some self-evident axioms, we can then rationally deduce further truths. So just as to recognise a circle depends on prior knowledge of what a perfect circle is, so to recognise a just act requires an insight into the nature of justice. 

According to Plato, the Form of the Good is: is self-evidently what people desire - the good life is what all people seek  the purpose of all action and the destination foundation of all excellence - the paradigm of right behaviour and the ideal reality an unchanging, constant, independent fact

As the Form of the Good does not exist in the physical realm one must discover it through reason - as one knows that a straight line is the shortest distance between two points and that what is A cannot also be what is not A. 

Evaluation: the nature of the Good seems to be visionary and mystical, rather than rational. Plato fails to adequately explain the form - resorting to allegories such as the Sun which commits the fact-value fallacy (the move from the Sun being the source of life - fact - to it being Good - value.  Plato's argument rests on synonyms: 'excellence', 'perfection' and 'ideal' that provide no substance to what 'the Good' consists of.  Plato ties in goodness and morality with performing a function in society. This is problematic as how well we do something can be distinguished from being virtuous, e.g. Roman Polanski is a good film director, but also molested a 13 year old girl. There is a critical confusion between the words 'function' and 'purpose', the former merely suggesting a cog in a machine whilst the later having overtones of value.  Critical confusion between 'the typical' and 'the ideal'. The Form of the Horse defines the typical horse but there are multiple variations of what the ideal horse is. Crucial distinction between the typical man and the ideal man. The criteria for the ideal horse varies in a way that the criteria for the perfect circle does not. 

The biggest problem with the Form of the Good theory of moral truth is that Plato assumes that if one knows the Good, then one automatically acts virtuously. Yet everyone is familiar with knowing what is good but doing the opposite. For Plato, this weakness of the will is as a result of ignorance, as the understanding of the Good is not complete. This would mean the only reason someone would bully/overeat/steal is as they do not know the damage they are doing. As Hume asserted when he argued 'reason is and ought to be the slave of the passions', reason itself moves nothing, only when it is allied to desire does it motivate action. 

Plato is not offering enlightened self-interest. It is not a matter of calculation that it is in self-interest to do good. Plato is arguing that to know the good is to be so attracted one acts morally, and therefore my self-interest coincides with the virtue. The motivating factor is the rational knowledge of the Form of the Good. Would it then be possible to know the Good yet not wish to pursue it? Does a proposition that is naturally true carry with it a prescriptive force?As in Aristotle's 'incontinent man' it is possible to possess knowledge yet ignore it. It is possible to know the truth yet be moved by appetite. 

Plato and the Form of the Good

Weakness of the will