Buddhism teaches that the law of cause and effect underlies the workings of all phenomena. Positive thoughts, words and actions create positive effects in the lives of individuals, leading to happiness. Negative thoughts, words and actions on the other hand--those that in some way undermine the dignity of life--lead to unhappiness. This is the general principle of karma.
In Buddhist teachings other than the Lotus Sutra, Buddhist practice is understood as a gradual journey of transformation. This is a process in which, over the course of many lifetimes, the essentially flawed and imperfect common mortal gradually molds and transforms him- or herself into a state of perfection--Buddhahood--through painstaking efforts to accumulate positive causes while avoiding negative ones.