Aristotle examined several different ethical values to discuss their merit as well as how to uphold them properly. He analyzes these virtues and states that he believes they arise from both our upbringing and our familiarity with them—that is, persistent practice of the virtue. On the other hand, he argues that vice is the absence of action toward one of these virtues: where we act without excellence.
Aristotle focused his efforts on the virtues of prudence, temperance, courage, and justice. He analyzed how each of these virtues is created and practiced throughout one's life and evaluated the merits and practical applications of each virtue as well as the associated vice.
One of the virtues he did not study was compassion, which is an essential virtue, particularly in the complex world in which we live today. Compassion is essential because it is used to ensure that people are treated kindly. Justice ensures that everyone receives their fair due, but compassion attempts to show love to other people.
The way to gaining compassion, if we are to follow Aristotle's prescription, is to see it from a young age and then to practice is as often as we can. By needing to see it from a young age, it becomes the responsibility of those around us to engender compassion; but once we see it, we can practice it. Practicing compassion would be showing kindness and gentleness to others as well as respecting their humanity. At times, it may mean showing forgiveness instead of doling out justice or retribution.
The vice that would most closely be associated with compassion is probably weakness. Someone who is compassionate can go overboard and be a weak target to be taken advantage of. Being virtuous means knowing the appropriate amount of compassion to be shown. Additionally, one must realize that showing compassion to someone may at times mean reprimanding them to help them improve or serving justice to someone else who has caused that person harm.