What the first proposition meant: no proximate power without efficacious grace
Thesis XVII. Whatever they made of that sense, what has been set out shows for certain that by those words Jansenius meant only this. At times, by a judgment of God that is hidden but just, certain believing and righteous people do not receive from God grace efficacious of itself for praying, for overcoming a temptation, or for keeping some commandment.
In that case, though they do have some will to keep the commandment, it is slight, feeble and imperfect, not equal to keeping it fully and as it should be kept. With the strength they have at that moment they are therefore not proximately and completely able to pray as they should, to overcome the temptation, or to keep the commandment as it should be kept. This inability, then, is simply the one that comes from weakness of will and from the absence of the efficacious aid that gives at once both the proximate and fullest ability and the willing.
Latin
XVII. Quicquid vero de illo sensu existimaverint, ex iis quae sunt exposita certum est, Jansenium verbis illis non aliud significatum voluisse, quam aliquando contingere, occulto sed justo Dei judicio, ut fideles & justi nonnulli a Deo non accipiant gratiam per se efficacem ad orandum, ad tentationem superandam, & ad praeceptum aliquod observandum: & tunc, licet habeant aliquam praecepti implendi voluntatem, sed parvam, invalidam, & imperfectam, & ad praeceptum illud plene & ut oportet observandum imparem, non esse illos, secundum praesentes quas habent pro isto momento vires, proxime & complete potentes, ad orandum ut oportet, ad tentationem superandam, & ad praeceptum ut oportet observandum. Adeoque hanc impotentiam non aliam esse nisi eam quae oritur a voluntatis infirmitate, & a carentia auxilii efficacis, quod simul & posse proximum ac completissimum, & velle donat.