Fr. Dulles presents the history of the medieval filioque theory fairly accurately, but alas what he never does in the article is to take into account the distinction between procession (ἐκπορεύεσθαι) and manifestation (φανέρωσις), which is why he never really addresses the criticism of the Eastern Church against the scholastic form of the filioque. That said, what he describes - somewhat disparagingly - as the "first Eastern alternative" to the filioque in the section of the article entitled "The Stakes" as the monopatrist view is in fact the faith of the ancient Orthodox Church, because the Greek Fathers, and it is important to remember that the Greek language is the language of the New Testament revelation of God, taught that the procession (ἐκπορεύεσθαι) of origin of the Spirit is only from the Father; while the Spirit's manifestation (φανέρωσις), i.e., what Gennadios Scholarsios called His gushing forth (άναβλυζειν), which must not to be confused with the existential origin of the Spirit, is from the Father through the Son. Now it would have been nice to see this theological distinction (i.e., the distinction between ἐκπορεύεσθαι and προϊέναι) made by Fr. Dulles, but alas he never addresses the actual doctrine of the East concerning the Spirit's procession (ἐκπορεύεσθαι) of origin and His manifestation (φανέρωσις), nor does he ever address the fact that the East restricts causality within the Godhead to the Father alone as monarch and font of divinity, for as St. Gregory of Nazianzus said: ". . . all that the Father has belongs likewise to the Son, except Causality." So after failing to ever really address the Eastern criticism of the medieval filioque theory Fr. Dulles next goes on to say that the so-called monopatrist position divides the economic Trinity from the immanent Trinity, but that accusation is simply false, because believing that there is a real distinction (πραγματικά διάκρισις) within God between economia and theologia does not necessitate positing a real division (πραγματική διαίρεσις) in God. Now clearly for the Scholastics this theological distinction was a problem, but that was because they accepted the dialectical approach of Aristotle, which ended up reducing the hypostatic properties of the Father, Son, and Holy Spirit to mere relations of opposition within the divine essence. But that late medieval Western theory was never accepted as legitimate by the Eastern Fathers, for whom there could be no opposition (διαλεκτικη or διάστημα) within the Godhead. Now with that out of the way, the third so-called "weakness" - to use Fr. Dulles' own phrasing - with the monopatrist position is that it becomes "hard to see how the Son and Spirit differ," but this is also a false dilemma, because the distinction between the Son and Spirit is affirmed by simply recognizing - as St. Maximos did in his letter to Marinus - that the Son takes His origin from the Father alone by γέννησιν while the Spirit receives His origin - again from the Father alone - by ἐκπόρευσιν (see also St. John Damascene, De Fide Orthodoxa, Chapter 8; and St. Gregory Nazianzus, Oration 31:8). Finally, at least as it concerns Fr. Dulles' assessment of monopatrist, he says that this focus upon the Father alone as cause, which by the way is the faith of the Orthodox Fathers, runs the risk of making the Son and Spirit "independent" agents within the Godhead, but there is no truth to this accusation either, because the Eastern Fathers always taught that the divine activity (ἐνέργεια) is one and simple within the Godhead flowing forth from the Father, through the Son, and in the Spirit, both temporally and eternally. In fact ultimately, the monarchy of the Father can only truly be affirmed if one holds that the Father alone eternally gives hypostatic existence to the other two persons of the Trinity, and that is why the Greek bishops at Florence proposed using St. Maximos' letter to Marinus as the decree of union on the issue of the filioque; but sadly their proposal - and the proposal presented by Gennadios Scholarios that I quoted above - was rejected by the Latin bishops in favor of what became the official Florentine decree, a decree that affirms causality to the Son in the existential origin of the Spirit's subsistence, and which confuses the Spirit's procession (ἐκπορεύεσθαι) with His progression (προϊέναι).
I will, when time permits, address the next point brought up by Fr. Dulles in his article, i.e., the Western attempts to equate the medieval theory of the filioque with the "per filium," and I will explain why these attempts will always - from an Eastern Christian perspective - fail.
God grant you many years,
P.S. - What Fr. Dulles calls "monopatrism," I call the "monarchy" of God the Father.