Plato on Justice:

    The concept is presented as a sort of harmony or balance of the elements both of the individual soul and the state.  Each part of the soul has its own particular and appropriate function, and the imbalance of the soul or the state is found in one part ruling over another where ruling is not the particular function or virtue of that part.
    The parts of the soul and the state are:
1.  Rational
2.  Spirited
3.  Appetitive

In both the state and the individual, justice is achieved with a harmony of these elements where the rational rules over the spirited which rules over the appetitive.  Justice is achieved in a sense by taking all the three virtues (wisdom, courage and temperance) and understanding their proper balance as constituting justice, which is the good of the individual being and the good of the state.
    Justice is thus a matter of knowledge (related to the notion in Plato's *Apology* understood as ethical determinism) such that knowing the good implies doing the good.  It is necessary for Plato that the ruling element of the soul be rationality, which is the highest faculty.  Further, in the political state, the wisest and best persons should rule, and so it is that those who are most fully acquainted with the real, and who can distinguish reality from appearances, are the best to rule.  In fact, they will be best to rule in part because it is what they least want to do.  But they will recognize their duty in ruling and will do well at it.

Aristotle on Justice:

    Justice is a virtue practiced toward other people, and it is the whole of virtue, not just part of it.  Just as the state is prior to the individual, so justice, being a virtue that is practiced toward others, is more related to the community than a particular virtue of some other name might be.
    The ways in which people associate with other constitute particular justice.  It is seen in distribution and in rectification.
    Distributed justice involves geometrical proportion.  If the unjust is unequal, then the just is equal.  What is equal is a mean, so justice is a mean and it always involves at least 4 terms:  2 people with 2 shares.  Shares are equal in the same ratio as the persons are equal.  If unequals recieve equal shares, or equals recieve unequal shares, it causes "quarrels and complaints.
    Rectificatory justice is found voluntarily and involuntarily.  In the voluntary sense, it is in selling, buying, interest and lending.  In the involuntary sense, it is found in theft, adultery, killing and assault, among other things.  Rectificatory justice involves arithmetical proportion.  The unjust action involves an unfair gain which the judge in an affair attempts to equalize.  So rectificatory justice is the mean between loss and gain.
    The function of a judge in a case is to restore equality that is lost in some sort of unfair transaction or occurrence.

    The most imortant point of inquiry is political justice in particular.  Political justice is a shared life for the satisfaction of needs as persons free and equal arithmetically or proportionately.  To be free is to be an end in oneself.  Justice only exists where mutual relations are controlled by law and law is found only among those liable to injustice.  This is why it is not a person who rules, but the law - because a person is likely to rule for his own advantage, not for justice - and justice is meant to be to the advantage of all.
 

St. Thomas Aquinas on Justice
    Continues in some sense the work of Aristotle in many ways, but combines with it the notion of an ultimate God as the highest object of happiness.  Aquinas does not deny that Aristotle was right in claiming that the highest good was happiness, but where Aristotle saw it as being possible to achieve happiness in this life, Aquinas held that true happiness will only be achieved in another life.  Of course, Aristotle didn't hold with the notion of there being another life.
    For Aquinas, justice is the highest of all moral virtues.  It is concerned with external actions and is found in the will for dealing with every aspect of our dealings with other people.

    Justice is a constant will to render to each person his right.  This refers to our relations with others and it is consistent with Aristotle's notion that a virtuous action must be done voluntarily, from a stable character, for the right reasons, and in the mean.

    Justice is a relation to another implying equality.  A thing cannot be equal to itself, but must be equal to something else.  So justice requires community of others.  Justice is only found in one person toward another.

    Justice is a virtue that makes the human being and the human act good.  Acts are good when they are rational and justice regulates actions, so it makes our actions good.

    Justice does not direct cognitive power because justice is not a matter of knowing.  It is instead a matter of doing, and doing is from appetite, so justice has to do with the will.

    Justice directs us to the common good, and so it is a general virtue.

    Justice is not about the passions, but about action.

    Justice is foremost among all the virtues because it concerns others and it is rational.
 
 

David Hume

    Justice is useful.  Public utility is the sole origin of justice.
        If we lived in abundance, there would be no distinctions of property - it would be held in common.  If we were all ruled by extreme friendship and benevolence, the notion of justice would be suspended.  There would be no distinctions between what is mine and what belongs to someone else.
    But rules of justice follow from the condition we are presently in.  If extreme abundance or want existed, or if people were perfectly moderate or rapacious, justice would be rendered useless.
    Imagine cases such as the "golden age" and the Hobbesian/Lockean States of Nature.  These conditions would render justice completely useless.  And even if all our possessions began in equality, art, care, and industry would cancel that equality and create conditions in which justice becomes a virtue to fill a need for purposes of utility.

    Statutes, customs and precedents create property  - the interest and happiness of human society is the point at which reasoning about justice terminates.  When we define property, a relation is found between occupation, industry, inheritance and so on - nature does not establish such things.
 
    Morality is not based on reason:
        1.  Reason judges matters of fact and relations, not morality, which is not an object of reason
        2.  When we make moral judgments, we do so always with sentiments of blame or approbation
        3.  "Reason is and ought only to be, the slave of the passions...."

    An example why virtue and vice cannot be matters of relations of ideas - the example of the seedling and the parent tree.
    Further, virtue and vice cannot be matters of fact - there is nothing in a moral claim indicating a fact that can be found by the senses.  All there is in a moral claim is passion.
    The morally good is what we ought to do and this is not found out by reason.

    Just as imagination is the ground of science, so affections are the ground of morality.

    We approve of virtuous qualities because we are moved by benevolence, humanity - moved by SYMPATHY - not pity, but fellow feeling.

    Hume argues against "selfish systems of morals":
        1.  They exaggerate the power of reason
        2.  Not all desires are always for one's own good.
        3.  Self-interest presupposes passions. Without desires other than one's own good, there wouldn't be anything to concern self-interest.
        4.  Self-interest is not the strongest or dominant passion.

Justice is an artificial virtue - a product of human contrivance and human need.
 

Kant and Mill may be done only in class....