In what sense was John Wesley a monergist? Here's a quote from Ken Collins' The Theology of John Wesley: Holy Love and the Shape of Grace (Abingdon, 2007). The quote is lengthy but well highlights an element in Wesley's theology that is often overlooked or misunderstood. Collins writes:
Wesley maintained that the monergistic reading (that is, the work of God alone) in one sense is accurate. Recall the language cited earlier: "'Nay, but we affirm, that God alone does the whole work, without man's working at all'; in one sense, we allow this also. We allow, it is the work of God alone to justify, to sanctify, and to glorify; which three comprehend the whole of salvation." In other words, Wesley intentionally sought to avoid the contradiction of affirming the monergistic and synergistic paradigms simultaneously by offering a distinction, a carefully thought-out qualification that was so very typical of his "third way" theological style. But this observation also means (and this is what has been missed by those who read Wesley utterly in a synergistic way) that Wesley did indeed think it appropriate to affirm the monergistic view at least in one sense because he recognized it carried meanings that are ever crucial to the proclamation of the gospel aright.
If, however, a nearly exclusive synergistic reading of Wesley's doctrine of salvation is offered (the "catholic" paradigm) and is drawn to tightly, neglecting the insights of the Protestant reformers, especially in terms of the sheer gratuity of grace, then the divine freedom itself will at least be misunderstood and possibly eclipsed. In this reckoning, once the initial or prevenient action of the Most High occurs, then God is virtually limited to responding merely to human response. But Wesley, as with Luther and Calvin, understood quite well that God is remarkably gracious and at times acts alone in the face of human impotence, for not only is justification not a human work but also the gift of grace is not given on the basis of a prior working.
So then, as noted earlier, the conjunctive style of Wesley's theology is not, after all, fully or aptly expressed in the divine and human roles found in an overarching synergistic paradigm even if the stress is on divine initiative (as in the model of responsible grace) for this is to privilege, once again, merely the "catholic" Wesley. On the contrary, more accurate readings suggest that a synergistic paradigm, which contains both divine and human acting, must itself be caught up in an even larger conjunction in which the protestant emphasis on the sole activity of God, apart from all human working, is equally factored in - not simply co-operant or responsible grace, but the conjunction of responsible and free grace, the union of both a catholic and protestant emphasis (163-4).