I will discuss and defend the following argument for concursus praevius (framed within the metaphysics of powers): (i) created powers are not essentially directed towards particular manifestations or effects (determinata ad hunc numero effectum), although they are essentially directed towards some kinds of manifestations; (ii) nevertheless created powers do somehow acquire the readiness for particular manifestations; (iii) no created factor can be responsible for this sort of determination; so (iv) it is God's concurrence of the concursus praevius type that produces the intrinsic readiness of a power for a given particular effect the power is going to produce. The argument is to be found e.g. in John of St. Thomas (Cursus philosophicus, Phil. nat., p. 1, q. 25, art. 2). What makes the argument particularly interesting is that some of its premises are quite widely accepted in scholasticism (see e.g. Suarez, Disp. met. 5, s. 9, n. 7-10, where he says of one of them: multis modernis scriptoribus doctissimis placere video), but also in some branches of analytical metaphysics of powers and action (e.g. Jonathan Lowe).
After a brief sketch of what I take to be the core of the concursus praevius controversy I will offer a reconstruction and a defence of the argument (both in the scholastic and in the contemporary analytic context).