Molina's account in the Concordia (q. 14, disp. 26): one action, from God by general concurrence and from the creature by particular influence
These points, and more of the same kind, are worked out and explained at greater length by Luis de Molina in his Concordia of free choice with the gifts of grace, question 14, disputation 26.
He states, first, that God concurs with secondary causes in their operations and effects in this way: just as the secondary cause directly produces its operation and through it brings about its result or effect, so God, by a general concurrence, flows directly together with it into that same operation and through the operation or action brings about its result or effect.
Second, when God concurs with secondary causes he acts as a universal cause, by an influence indifferent to various actions and effects, and that general influence is determined to different kinds of action and effect by the particular influence of secondary causes, which differs according to the different power each has to act. The sun's influence, which is likewise universal, is determined by a man's influence to produce a man and by a horse's influence to produce a horse. If the cause is free, it is in its power to exert its influence so that this action rather than that results, say willing rather than refusing, or walking rather than sitting, and this effect rather than that, this artefact rather than another. Or it can withhold its influence altogether, so that there is no action at all.
Third, God's influence through universal concurrence is not enough to produce any effect without the influence of the particular secondary cause that determines it. Nor, conversely, is the particular cause's influence enough without God's influence through universal concurrence, which helps it and which by ordinary law God has resolved never to withhold. These two influences depend on each other in order to exist in reality; indeed they are not two actions but numerically one action. As it comes from God acting in that way it is called general concurrence; as it comes from the secondary cause, say from fire heating something, it is called the concurrence or influence of the fire. And that action is of this kind, heating rather than cooling, not because it comes from God through universal concurrence but because it comes from the fire, with God cooperating, through the fire's particular power.
Latin
XXX. Haec & plura ejusdem generis prolixius diducta & exposita videre est apud Ludovicum Molinam in Concordia Liberi Arbitrii cum gratiae donis, &c. quaest. 14. disputat. 26. Ubi affirmat primo Deum ita cum causis secundis concurrere ad earum operationes & effectus, ut quemadmodum causa secunda immediate elicit suam operationem, & per eam terminum, seu effectum producit; sic Deus concursu quodam generali immediate influat cum ea in eandem operationem, & per operationem, seu actionem terminum illius, seu effectum producat. Secundo, Deum, quando concurrit cum causis secundis, influere ut causam universalem, influxu quodam indifferenti ad varias actiones & effectus, determinari vero influxum illum generalem ad diversas species actionum & effectuum a particulari influxu causarum secundarum, qui pro diversitate virtutis cujusque ad agendum diversus est. Non secus ac influxus solis, qui etiam universalis est, determinatur ab influxu hominis, ut producatur homo; & ab influxu equi, ut oriatur equus. Quod si causa libera sit, in ipsius potestate esse ita influere, ut producatur potius haec actio quam illa, puta velle, quam nolle, aut ambulare, quam sedere, & hic effectus potius quam ille, nempe hoc artefactum, potius quam aliud; Vel etiam suspendere omnino influxum, ne ulla sit actio. Tertio, ad nullius effectus productionem satis esse influxum Dei per concursum universalem, sine influxu causae secundae particularis a qua determinatur, neque vicissim influxum causae particularis, sine influxu Dei per concursum universalem, quo adjuvetur, & quem de lege ordinaria statuit nunquam denegare. Hos vero duos influxus mutuo ab invicem pendere, ut in rerum natura existant: imo non esse duas actiones, sed unam numero actionem, quae ut est a Deo illo modo influente, dicitur concursus generalis; ut vero a causa secunda, puta ab igne calefaciente, dicitur concursus, seu influxus ignis. Neque actionem illam habere quod sit hujus speciei, nempe calefactio, potius quam frigefactio, quia est a Deo per concursum universalem, sed quia est ab igne cum Deo cooperante per suam particularem virtutem.