I thoroughly enjoyed this book and was very impressed by the breadth and depth of the scholarship. Its thesis is that along with Kant's epistemological concerns an interest in freedom was partly responsible for generating his mature philosophy. This is, I think, an under appreciated fact amongst non-specialists in Kant. All we usually hear about is the revolutionary first Critique so this is an important thesis and opened my eyes to a major side of Kant's whole project.
The book also unearths the theological background to Kant's thinking that shapes the problem he is tackling: how humans can be free given they relate to a god. In tracing the dimensions of this problem and Kant's changing thinking about it, Insole provides exegetical illumination over a very wide range of texts (some from the German), accounts for chronology and shifts in Kant's thought, and offers careful reconstruction of the arguments. It is very impressive scholarship: incisive and insightful, dealing with manifold of primary literature, opening up new aspects and nuances of Kant's thought. It also, I felt, rehabilitates Kant within theology; as recent theology has been unfair to Kant in various ways. This was again very helpful as it not only offers a case study in the theological nature/elements of enlightenment philosophy but also offers a more nuanced picture of Kant than his famous attack on the proofs for God's existence suggests.
A favourite part of the book for me was the handling of Trendlenberg's 'neglected alternative', which Insole shows to be not so much neglected as intentionally refused by Kant because it falls foul not so much of Kant's epistemological concerns as his interest in freedom. For those not so into Kant but interested in theology, the later chapters discussing different versions of the relation between divine and human will, causation and freedom offers fascinating reading and masterly summaries of a great deal of complex material. The material is highly controlled throughout; the argument moves along at a good pace, neither too slow nor too fast. The writing is very clear as is the structure of the argument, so despite the subtlety of the material I never felt lost. Highly recommended.
This is an outstanding look at Kant's lifelong wrestling with one of the central questions in philosophical theology: how and where is the balance to be struck between God's agency and creaturely autonomy (especially human freedom)? Stress the divine side, and you risk the prospect of complete causal determination by God - i.e. occasionalism. Stress the creaturely side, and you end up with God as an absentee landlord (deism) who soon becomes - surprise surprise - an absentee.
Once one looks through the lens of this and related problems, it's amazing how much light they shed on Kant's critical turn. It's difficult to condense Insole's arguments, but in effect once God is made quietly redundant behind the noumenal curtain, our concepts + raw sense-experience takes over several of his theoretical roles. In doing so, we become the "creators" of everything in front of the noumenal curtain - space, time, causation, substance, etc. - in such a way that we can intelligibly say we're not stuck in a causal groove determined by anything other than us. And this is what solves the problem of reconciling human freedom to divine superintendence. Needless to say, the substitution comes at a heavy explanatory cost, and Insole shows how Kant is alert to and occasionally explicit about these.
But all this only emerges once one looks at Kant 'in the round" - i.e. analyses seriously the role God plays in his early pre-critical thought. Insole is part of a (very) small handful of young scholars who are quietly changing the terms of the debate on Kant and religion, in large part by focusing on this topic in his writings over the neglected period prior to 1770. Until recently the debate had been fought mainly around the only work devoted explicitly to religion, i.e. "Religion Within the Limits of Reason Alone" (1793). Now when viewed through this prism alone, Kant becomes a classic Aufklärer / Enlightenment Man on religion, especially as regards its outward expressions (though I suspect that had at least as much to do with his pietist upbringing). But this sort of hand-wringing over Kant's negative stance towards institutional religion in a single text (and one that triggers many tensions with the critical stances) became increasingly technical, heated, and fruitless.
The conversation was stalled until Insole and others (Andrew Chignell, Desmond Hogan, Eric Watkins) started serious work on "theistic" problems in Kant's pre-critical thought. In this book, as well as some accompanying academic articles, Insole shows that once you bring in Kant's vast early output (he was 56 or so, after all, when this happened), you see how his wrestling with crucial metaphysical questions in *philosophical theology* significantly shapes his later thought. There is rupture from this, of course: in fact, if Insole is to believed, the rupture *itself* is Kant cutting the Gordian Knot of the problem of divine action. But there are deep and unmistakable lines of continuity too, which tend to be ignored by those who are tone-deaf to Kant's sophisticated theistic stances in the early period. This new perspective helps us to see Kant's solutions to the problem of causation in particular through a new filter. Insole also digs deep into the many lectures Kant was delivering over the course of the critical period, and extracts many useful nuggets for those trying to understand the three Critiques as a whole.
The conclusion offers the tantalising suggestion that the limits Kant puts on thought and talk about God are not so different from those put on him in the scholastic period - Aquinas is as clear as Kant that creaturely beings cannot know how God is "in se" (or, perhaps, "an sich"?). If that is right, then theists sympathetic to the classical tradition may realise there is little to worry them in Kant's strictures. In fact, they might even help theologians to be more hygienic in their own thought and talk about God.
Incidentally, I found the ideas in this book very useful for teaching Kant and explaining transcendental idealism to AS/A2 students and undergraduates.