Brian Leftow

In The Metaphysics of Creation and The Metaphysics of Theism, Norman Kretzmann defends an argument for God's existence which he claims to find in Aquinas. I assess this argument's key premise, a principle of sufficient reason, that: ‘PSR2: Every existing thing has a reason for its existence either in the necessity of its own nature or in the causal efficacy of some other beings’. PSR2 requires God's nature to explain His existence. Kretzmann does not tell us how this explanation is supposed to go. I examine such ways as I can envision that God's own nature might explain His existence. None pan out. I argue contra Kretzmann that if God is simple, as Aquinas understood this, His nature does not explain His existence, and while His existence is in itself per se notum (‘self-evident’) this does not entail that it has an explanation. If this is correct, we ought not to read Aquinas as committed to PSR2. Further, if I'm right that it's impossible for ‘the necessity of a thing's nature’ to explain its existence, PSR2 is true only if every existing thing has a reason for its existence in the causal efficacy of some other beings. So, if I'm right, theists ought to steer clear of PSR2, at least read in terms of genuine explanation. I finally offer a weaker reading of ‘a reason for its existence’ which does not generate the problems of the stronger reading Kretzmann seems to have in mind. This too, though, turns out to have its problems.

Brian Leftow offers a theory of the possible and the necessary in which God plays the chief role, and a new sort of argument for God's existence. It has become usual to say that a proposition is possible just in case it is true in some 'possible world' (roughly, some complete history a universe might have) and necessary just if it is true in all. Thus much discussion of possibility and necessity since the 1960s has focussed on the nature and existence (or not) of possible worlds. God and Necessity holds that there are no such things, nor any sort of abstract entity. It assigns the metaphysical 'work' such items usually do to God and events in God's mind, and reduces 'broadly logical' modalities to causal modalities, replacing possible worlds in the semantics of modal logic with God and His mental events. Leftow argues that theists are committed to theist modal theories, and that the merits of a theist modal theory provide an argument for God's existence. Historically, almost all theist modal theories base all necessary truth on God's nature. Leftow disagrees: he argues that necessary truths about possible creatures and kinds of creatures are due ultimately to God's unconstrained imagination and choice. On his theory, it is in no sense part of the nature of God that normal zebras have stripes (if that is a necessary truth). Stripy zebras are simply things God thought up, and they have the nature they do simply because that is how God thought of them. Thus Leftow's essay in metaphysics takes a half-step toward Descartes' view of modal truth, and presents a compelling theist theory of necessity and possibility.

Jeff Speaks’s The Greatest Possible Being criticizes several sorts of perfect being theology. I show that his main discussions target what are really idealizations of actual perfect-being projects. I then focus on whether Speaks’s idealizations match up with the real historical article. I argue that, in one key respect, they do not and that it would be uncharitable to think that one of them does. If the idealizations do not represent what perfect being thinkers have actually been doing, a question arises about how much Speaks’s critique should worry those pursuing projects modelled on real historical perfect being theology.

Most debate in the philosophy of religion centres on “thin theism,” the thesis that there is a deity who is omnipotent, omniscient, etc. But few if any theists are just thin theists. For most, thin theism is at best the abstract skeleton of a fuller set of religious beliefs— Christian, Jewish, or Moslem. Thus, there is another set of issues philosophers of religion might but rarely do discuss: with what sort of warrant might one add to thin theism the beliefs of a particular religious tradition? In other words, supposing that thin theism is true, what reasons might there be to be, say, a Christian? Is Christianity True? takes up this last question. Successive chapters ask whether there would be moral benefit in worshipping the Christian God, whether it is reasonable to accept Christianity’s distinctive claims though other traditions which embed thin theism deny them, whether the doctrine of the Incarnation makes sense, whether the doctrine of the Atonement is morally acceptable, whether we know enough about Jesus’s sayings and doings to warrant Christian claims about him, whether the doctrine of the Trinity is coherent, and whether there is a coherent conception of life after death; an appendix takes up Marx on religion.

Jeff Speaks has recently argued that perfect being theology treating God as the greatest possible being—he calls it alethic perfect being theology—cannot deliver new information about God. This argument is central to his critique of all forms of perfect being theology. For as Speaks sees it, other forms of perfect being theology may collapse into alethic perfect being theology, i.e. fail in the end to be a different sort of project. I lay out how he understands alethic perfect being theology and then contest his argument.

Before Duns Scotus, most philosophers agreed that God is identical with His necessary intrinsic attributes--omnipotence, omniscience, etc. This Identity Thesis was a component of widely held doctrines of divine simplicity, which stated that God exemplifies no metaphysical distinctions, including that between subject and attribute. The Identity Thesis seems to render God an attribute, an abstract object. This paper shows that the Identity Thesis follows from a basic theistic belief and does not render God abstract. If also discusses how one might move from the Identity Thesis to the full doctrine of divine simplicity and shows that the Identity Thesis generates a new ontological argument