In general, moral discipline is a virtuous determination to abandon any non-virtuous action. For example, if by seeing the disadvantages of killing, stealing, or sexual misconduct we make a firm decision to refrain from such actions, this is moral discipline.
Similarly, the determination to refrain from lying, divisive speech, hurtful speech, idle gossip, covetousness, malice, and holding wrong views is also moral discipline.
In Pratimoksha Sutra, Buddha says that it would be better for us to die than to break our moral discipline, because death destroys only this one life, whereas breaking our moral discipline destroys our opportunity to experience happiness in many future lives and condemns us to experience the sufferings of lower rebirths over and over again.
Cause of happiness
In Buddhist countries, moral discipline is regarded as very important, and it is for this reason that monks and nuns are held in such high esteem. However, it is not only monks and nuns who need to practice moral discipline; everyone needs to practice moral discipline because it is the root of all future happiness.
The practice of moral discipline is the main cause of rebirth as a human. If we practice moral discipline by abandoning negative actions, such as killing, with the motivation to obtain human happiness, this moral discipline will protect us from lower rebirth and cause us to be reborn as a human being in the future.
If we practice moral discipline with a sincere wish to attain liberation for ourself, or full enlightenment for the sake of all living beings, this is higher moral discipline.
Three types of moral discipline
There are three types of higher moral discipline: Pratimoksha moral discipline, Bodhisattva moral discipline, and Tantric moral discipline. These types of moral discipline are distinguished by the motivation with which they are practised and the particular downfalls that they abandon.
Pratimoksha moral discipline is motivated mainly by the aspiration to attain personal liberation, Bodhisattva moral discipline mainly by bodhichitta, and Tantric moral discipline mainly by special Tantric bodhichitta.
There are three types of vow associated with these three types of moral discipline.
Not every practice of moral discipline entails taking vows. For example, if we realize the many faults of killing and, as a result, make a strong decision to abstain from killing, we are practising moral discipline even though we have not taken a vow.