Calixtus: the power to believe is given, but no necessity
Thesis XVIII. This is Georg Calixtus's doctrine in the judgment already cited on the controversies in dispute between the Lutherans and the Reformed, number 32. There he first establishes that the Gospel is God's appointed instrument for imparting faith and salvation to people. With it, as it enters the mind through the ears, supernatural divine grace is joined, and through that grace a person who, left to himself, could not before give assent and faith is now able to.
Then he adds: 'He thus gains the power of believing that he lacked before, yet no necessity binds him, for if he gives free rein to his disposition and depravity, he can resist and struggle against the Holy Spirit and drive away the word of God...
That a person who hears and weighs the Gospel believes, or even can believe, must be credited not to the powers of nature but to the grace bound up with the Gospel and supplied through it. That he can withstand grace must be blamed on his inborn depravity and disposition. Since God is indeed efficacious and at work through his grace, though not by absolute power but by a power that allows for conditions and order, it follows that he can be thwarted in the result and outcome.'
Latin
XVIII. Quae est doctrina Georgii Calixti in citato judicio de Controversiis quae inter Lutheranos & Reformatos agitantur numero 32. Ubi postquam constituit Evangelium esse organum divinum ad fidem & salutem hominibus impertiendum destinatum, cum quo per aures ad mentem immisso conjuncta est gratia divina supernaturalis, per quam praestatur, ut homo qui sibi relictus pridem non poterat assensum & fidem praebere jam possit, subjungit, Facultatem itaque credendi, qua destitutus ante erat, consequitur, necessitate tamen nulla astringitur, quia si indoli & pravitati suae fraenos laxat, potest obsistere & obniti Spiritui Sancto, & Verbum Dei repellere ..... Quod itaque homo Evangelium audiens & considerans credat, imo credere possit, acceptum ferendum est, non naturae viribus, sed gratiae cum Evangelio connexae, & per illud suppeditatae: quod autem gratiae possit refragari, congenitae pravitati & indoli imputandum. Quia enim per gratiam quidem suam Deus efficax est & operatur, non tamen potentia absoluta, sed conditiones & ordinem admittente, inde fit quod successu & eventu frustrari possit.