The ideas on what exactly constituted this "liberating insight" evolved over time. Initially the term "prajna" served to denote this "liberating insight." Later on, "prajna" was replaced in the suttas by the four truths. This happened in those texts where "liberating insight" was preceded by the four jhanas, and where this practice of the four jhanas then culminates in "liberating insight." The four truths were superseded by "pratityasamutpada", and still later, in the Hinayana schools, by the doctrine of the non-existence of a substantial self or person. And Schmithausen states that still other descriptions of this "liberating insight" exist in the Buddhist canon: