Molinists against Jansenius: grace in the will's power
Thesis IX. On this point Jansenius has many followers, namely those who call themselves disciples of Augustine in a special sense. Even so, this teaching of his is rejected by most of the Roman School. Both the followers of the method and teaching of Molina the Jesuit and those called the recent Thomists openly oppose it.
The first group hold that the grace of Christ, no less than the grace given to the first man before he fell, is in the will's power in such a way that, by its inborn liberty, the will can use it or not use it, and in fact often does not.
So, on their view, it depends on free choice whether Christ's grace is efficacious or not, and whether it achieves its effect in a man's conversion or fails to.
Latin
IX. Verum quanquam hac in parte Jansenius multos sectatores habeat, eos nempe qui singulari modo se discipulos Augustini vocant, haec tamen illius doctrina rejicitur a maxima Scholae Romanae parte: eique palam repugnant, tam qui Molinae Jesuitae Methodum & doctrinam sequuntur, quam qui recentiores Thomistae appellantur. Nam priores illi volunt gratiam Christi, non minus quam gratiam primo homini nondum lapso collatam, sic in potestate voluntatis esse, ut pro innata libertate, illa uti, vel non uti possit, & reipsa saepe non utatur: adeoque a libero arbitrio pendere, ut gratia Christi sit efficax, vel non efficax; & effectum suum in hominis conversione obtineat, vel non obtineat.