His teachings which were heavily into the concept of predestination led people to believe that humans are predetermined by God into salvation or damnation.
The relevant scriptural texts if interpreted as the 'foreknowledge of God' rather than the 'predestination of God' leave room for the concepts of freewill and salvation.
Sadly, Jansen would not have agreed - nor would John Calvin have been exactly sympathetic within protestantism!
(The belief system was heavily attacked by L'Abbé Prévost in his novel " L'histoire du chevalier des Grieux et de Manon Lescaut" on which the famous opera is based.)