 Bronkhorst notes that the conception of what exactly this "liberating insight" was developed throughout time.Whereas originally it may not have been specified, later on the four truths served as such, to be superseded by "pratityasamutpada", and still later, in the Hinayana schools, by the doctrine of the non-existence of a substantial self or person.And Schmithausen notices that still other descriptions of this "liberating insight" exist in the Buddhist canon