The cover illustration for The Challenges of Divine Determinism is a painting by Caspar David Friedrich, in which a lone, robed figure – a monk – stands looking over a bluff at a dark and turbulent sea. Above the sea looms a heavy cloud, which gradually thins as we look upwards, with a few patches of blue showing near the zenith. But where in this picture do we find divine determinism? Is it in the threatening sea, or in the cloud hanging over it, or perhaps in the shreds of blue far overhead?

Peter Furlong's attempt to answer this question takes the form of a section devoted to each of the main kinds of objections to divine determinism. In each case, he tries to arrive at the strongest formulation of the objection, and then to select or devise the best possible reply. In doing this he keeps in mind the distinction between two different kinds of divine determinism. ‘Edwardsian divine determinism’ is a view in which natural determinism operates, and the initial state (together with whatever later divine interventions there may be) determines the entire subsequent history. ‘Primary divine determinism’, in contrast, holds that nature may be indeterministic, but that God directly causes each and every creaturely activity, including those that are ‘free choices’. At numerous points he considers whether one or the other of these types of divine determinism is in a better position to respond to the objections that have been raised against divine determinism in general.

It might occur to us to wonder why there is not an equally detailed treatment of the reasons in favour of divine determinism. Furlong's answer is that including this would require several books in order to assess all of the issues which arise in the discussion of these reasons. However, in the first chapter he does survey some of the reasons that have been urged in support of the view, but without the detailed development and assessment devoted to the objections.

The objections considered include the ‘Consequence Argument’ against compatibilism, ‘Manipulation Arguments’, the claim that determinism makes God the author of sin, the claim that it makes God blameworthy for the sins and evils that occur, the claim that determinism undermines both the integrity of both God's love for human beings and the love of human beings for God, and several others. It is fair to observe that, in many cases, Furlong fails to find a response based on assumptions that are widely accepted or readily seen as plausible. At many points he speaks of the ‘costs’ of various responses – propositions needed for the response, which might otherwise seem implausible or unattractive. On two occasions he proposes a disjunction of possible replies (each admitted to be not especially attractive) as having sufficient probability to warrant rejecting the objection. An observation concerning an answer to an objection from Katherin Rogers would apply in other cases: ‘Even if such considerations do not decisively rebut Rogers's objection, they do offer the possibility of a reasonable response. In any case, such considerations are the best that the divine determinist can do’ (p. 194).

What is the upshot of all this? For Furlong himself, the outcome is agnosticism, both about the compatibility of determinism and free will, and about the truth of divine determinism (though he remains a theist). Probably relatively few will be satisfied with such a conclusion: too much else in one's worldview hinges on divine determinism, one way or the other. Nor does it seem likely that the book will result in many conversions. The issue of divine determinism, pro and con, is one on which convictions tend to be deeply ingrained and tenaciously held, in a way that is resistant to contrary arguments. What is clear is that theists of all stripes should be grateful to Furlong for his careful and insightful work. Determinists will be pleased that he has teased out the best, or some of the best, answers to the challenges; libertarians will note with satisfaction the limitations of those answers. But if we seek to locate divine determinism in Friedrich's painting, this reviewer is convinced we must be prepared to plunge into the black, icy waters.