Aristotle devotes Book V of the Nicomachean Ethics to justice (this is also Book IV of the Eudemian Ethics). In this discussion, Aristotle defines justice as having two different but related senses—general justice and particular justice. General justice is virtue expressed in relation to other people. Thus the just man in this sense deals properly and fairly with others, and expresses his virtue in his dealings with them—not lying or cheating or taking from others what is owed to them.
Particular justice is the correct distribution of just deserts to others. For Aristotle, such justice is proportional—it has to do with people receiving what is proportional to their merit or their worth. In his discussion of particular justice, Aristotle says an educated judge is needed to apply just decisions regarding any particular case. This is where we get the image of the scales of justice, the blindfolded judge symbolizing blind justice, balancing the scales, weighing all the evidence and deliberating each particular case individually.