本因妙 (Jpn honnin-myo )
Also, the mystic principle of the true cause. One of the ten mystic principles of the essential teaching (latter half) of the Lotus Sutra formulated by T'ient'ai (538-597) in The Profound Meaning of the Lotus Sutra. It refers to the practice that Shakyamuni carried out countless kalpas in the past in order to attain his original enlightenment. The term contrasts with the true effect, or the original enlightenment Shakyamuni achieved countless kalpas before his enlightenment in India. The true cause is indicated by the phrase in the "Life Span" (sixteenth) chapter of the Lotus Sutra, "Originally I practiced the bodhisattva way..."
Profound Meaning defines "bodhisattva way" as the true cause of Shakyamuni's original enlightenment. Shakyamuni did not clarify, however, what the bodhisattva way was. T'ient'ai interpreted it as a reference to the first stage of security, or the eleventh of the fifty-two stages of bodhisattva practice, i.e., the stage of non-regression, the attainment of which he defined as the true cause for Shakyamuni's original enlightenment. However, what teaching or Law Shakyamuni had practiced to attain the stage of non-regression remained unclear. Nichiren (1222-1282) identified the true cause, or fundamental Law, that enables all Buddhas to attain their enlightenment, as the Law of Nam-myoho-renge-kyo. Because he fully revealed the true cause for attaining Buddhahood and established a universal way of practice, in his lineage Nichiren is called the teacher of the true cause, while Shakyamuni is called the teacher of the true effect.