Schmid and Linford provide something like the following template for generating a classical theistic persistence proof (at 7–8):
1. There are Ts.
2. Ts require per se T-sustaining efficient causes.
3. Chains of per se T-sustaining efficient causes do not loop.
4. Chains of per se T-sustaining efficient causes do not infinitely regress.
5. (So) Chains of per se T-sustaining efficient causes have first members that are not Ts.
A particular classical theistic persistence proof may well have further premises from which the instances of the premises in this template are (claimed to be) derived. Further, in a particular classical theistic persistence proof, it may be that, in 3 and 4, ‘do not’ is replaced by ‘cannot’. It is worth noting that all we need for the validity of any given proof is the ‘do not’ claim. It is also worth noting that, in any given case, it might be supposed that the ‘do not’ claim is most strongly supported by the ‘cannot’ claim. Finally, it is worth noting that, in particular cases, we might debate whether or not to insist that the T-sustaining efficient causes are per se T-sustaining efficient causes.
Here are some examples of classical theistic persistence proofs that Schmid and Linford discuss:
A. Aristotle (Unmoved Mover)
1. There are movers.
2. Movers require per se movement-sustaining efficient causes.
3. Chains of per se movement-sustaining efficient causes do not loop.
4. Chains of per se movement-sustaining efficient causes do not infinitely regress.
5. (So) Chains of per se movement-sustaining efficient causes have first members that are not movers.
B. Aquinas (First Way)
1. There are changings.
2. Changings required per se change-sustaining efficient causes.
3. Chains of per se change-sustaining efficient causes do not loop.
4. Chains of per se change-sustaining efficient causes do not infinitely regress.
5. (So) Chains of per se change-sustaining efficient causes have first members that are not changings.
C. Feser (Aristotelian Proof)
1. There are potential-existence-realizations.
2. Potential-existence-realizations require per se potential-existence-realization-sustaining efficient causes.
3. Chains of per se potential-existence-realization-sustaining efficient causes do not loop.
4. Chains of per se potential-existence-realization-sustaining efficient causes do not infinitely regress.
5. (So) Chains of per se potential-existence-realization-sustaining efficient causes have first members that are not potential-existence-realizations.
D. Feser (Neo-Platonic Proof)
1. There are composites.
2. Composites requires per se composition-sustaining efficient causes.
3. Chains of per se composition-sustaining efficient causes do not loop.
4. Chains of per se composition-sustaining efficient causes do not infinitely regress.
5. (So) Chains of per se composition-sustaining efficient causes have first members that are not composites.
E. Feser (Thomistic Proof) and Aquinas (De Ente Proof)
1. There are essence-existence-composites.
2. Essence-existence-composites require per se essence-existence-composition-sustaining efficient causes.
3. Chains of per se essence-existence-composition-sustaining efficient causes do not loop.
4. Chains of per se essence-existence-composition-sustaining efficient causes do not infinitely regress.
5. (So) chains of per se essence-existence-composition-sustaining efficient causes have first members that are not essence-existence composites.
F. Feser (Rationalist Proof)
1. There are contingents.
2. Contingents require per se contingency-sustaining efficient causes.
3. Chains of per se contingency-sustaining efficient causes do not loop.
4. Chains of per se contingency-sustaining efficient causes do not infinitely regress.
5. (So) chains of per se contingency-sustaining efficient causes have first members that are not contingents.
Schmid and Linford assign Aquinas's First Way to a different category, on the grounds that it is concerned with change rather than with existence. I am not persuaded that this assignment is optimal. Schmid and Linford also discuss Feser's Augustinian Proof. I agree that this is quite a different beast; I shall have nothing more to say about it in this review. Schmid and Linford suggest (at 8) that Feser's Thomistic Proof and Aquinas's De Ente Proof have the same overall structure even though they also maintain (236ff.) that the details of the two proofs differ considerably. Finally, it is worth noting that we should at least discuss whether Aquinas's First Way is better formulated taking explicit account of respects in which change occurs:
G. Aquinas (First Way)
6. There are R-changings.
7. R-Changings required per se R-change-sustaining efficient causes.
8. Chains of per se R-change-sustaining efficient causes do not loop.
9. Chains of per se R-change-sustaining efficient causes do not infinitely regress.
10. (So) Chains of per se R-change-sustaining efficient causes have first members that are not R-changings.
There are several kinds of criticisms that Schmid and Linford make of classical theistic persistence proofs.
First, there are worries about the strength of the conclusions of these various proofs. The ambition of proponents of classical theistic persistence proofs is to establish that, at the foundation of reality lies pure act: unique, simple, timeless, immutable, impassible Existence untainted by potentiality. But, according to Schmid and Linford (a) conclusions of the classical theistic persistence proofs fall far short of delivering this claim, and (b) attempts by classical theists to advance to this claim from the conclusions of the classical theistic proofs all fail (§2.4 and chapter 8).
It is worth looking at the first things that feature in the conclusions of the classical theistic persistence proofs: (a) movers that are not moving; (b) causes of change that are not changing (or perhaps causes of R-change that are not R-changing); (c) causes of potential existence realization that are not potential existence realizations; (d) sustainers of composition that are not composites; (e) sustainers of essence-existence composites that are not essence-existence composites; and causes of contingents that are not themselves contingent. There is a big gap between movers that do not move and simple, timeless, immutable, impassible Existence untainted by potentiality. (Not moving does not entail unmovable.) There is a big gap between causes of R-change that are not R-changing and simple, timeless, immutable, impassible Existence untainted by potentiality; and there is also a big gap between causes change that are not changing and simple, timeless, immutable, impassible Existence untainted by potentiality. (Unchanging does not entail unchangeable; R-unchanging does not entail R-unchangeable.) There is a big gap between non-potential-existence-realization and simple, timeless, immutable, impassible Existence untainted by potentiality. (Not realizing potential existence does not entail simple and timeless.) There is a big gap between non-composition and simple, timeless, immutable, impassible Existence untainted by potentiality. (Not composite does not entail timeless.) There is a big gap between non-contingency and simple, timeless, immutable, impassible Existence untainted by potentiality. (Not contingent does not entail immutable, impassible, timeless, or simple.) Of course, quite apart from these problems, there is also the difficulty that, in general, the conclusions of the classical theistic persistence proofs only claim that there are things of a certain kind. To get from there to the claim that there is exactly one thing of the given kind is also a significant stretch.
Second, there is a general worry about the second premise in each of the classical theistic persistence proofs. An alternative to the second premise in each of the classical theistic persistence proofs is provided by an existential inertia thesis of something like the following form (84):
For any time t, for any T that exists at t*< t: (1) if T is not positively destroyed in the interval [t*, t], then T exists at t; and (2) at t, T does not concurrently ontologically depend on anything but the existence and activity of its own parts.
As Schmid and Linford note in chapter 5 (‘Existential Inertia: Thesis and Taxonomy’), there are many things to nail down in the provision of a thesis of existential inertia:
What does T range over? (108–111)
What is the modal status of the thesis? (116)
What is ontological dependence? (116–117)
What is positive destruction? (117–119)
What is persistence? (111–115) What is the metaphysics of inertial persistence? (119–125)
What is the relevant temporal ontology? (125–126).
Schmid and Linford offer a range of possible accounts of the metaphysics of inertial persistence in chapter 6 (‘The Metaphysics of Existential Inertia’). These include:
1. Tendency/Disposition: T has a tendency or disposition to continue in existence; so T will continue in existence unless that tendency or disposition is positively thwarted. (132–138)
2. Transtemporality: If nothing destroys T at t and there is some interval (t−, t) in which T exists and is not subject to sufficiently destructive factors, then T exists at t. (138–160)
3. Law: Successive states of T are generated from prior states by, or in virtue of the operation of, physical law. (161–162)
4. Necessity: The persistence of other concrete objects is explained by the existence of some fundamental, temporal, necessarily existent objects in which those other objects are grounded, or from which those other objects are composed, or by means of which those other objects are realized, or the like. (162–176)
5. No Change: Persistence is stasis: absence of change. In the absence of sufficiently destructive factors, nothing more is required for the persistence of T. (176–183)
Schmid and Linford claim that there are good motivations for adopting some thesis of existential inertia (EIT). In particular, they claim that the prominent rival hypothesis in this dialectical context – Classical Theistic Sustenance Thesis (CTST) – is theoretically inferior. (Roughly, CTST says that all temporal concrete objects are immediately annihilated in the absence of sustenance/conservation from without by simple, timeless, immutable, impassible existence untainted by potentiality.) Schmid and Linford argue – plausibly – that EIT is simpler than CTST and also better explains and unifies a range of disparate observations: that objects persist rather than suffer annihilation at arbitrary points in time; that objects cease to exist only when causally destroyed; that we have no observations of divine sustaining causes; and that our ordinary everyday explanatory and scientific reasoning is in good order (190–196). Schmid and Linford discuss a number of other motivations for adopting some thesis of existential inertia (190–208). And they claim that EITs can be defended from the principal criticisms that have been levelled against them (209–260). I shall not attempt to discuss any of that material in this review.
It is worth reviewing the second premises in the classical theistic persistence proofs in the light of discussion of existential inertia. These premises say that sustaining causes are required for the persistence of: (a) motion; (b) change (or R-change); (c) realization of potential existence; (d) composition; (e) essence-existence composition; and (f) contingency. (For the sake of the coming discussion, I shall simply assume that motion is non-inertial motion.) I think that it is obvious that the tendency/disposition, transtemporality, and no-change accounts of existential inertia straightforwardly entail the falsity of all of the second premises set out above. I also think that matters are not quite so straightforward in the case of the law and necessity accounts of existential inertia. Note, in particular, that if there are fundamental, temporal, necessarily existent objects in which those other objects are grounded, or from which those other objects are composed, or by means of which those other objects are realized, or the like, then we do have sustaining causes/grounds for realization of potential existence (and perhaps we also have sustaining causes in some of the other cases as well).
Contemporary philosophers who feature in the discussion in this work include Feser, Hsiao and Sanders, Kerr, McNabb and DeVito, and Nemes. Feser's Five Proofs looms particularly large: discussion of Feser's Augustinian proof (and theistic conceptualism) (chapter 10) appears because it is in Feser's book, and not because it is a classical theistic persistence proof. Throughout, Schmid and Linford take the context for the discussion to be dialectical: the onus is on the proponents of the classical theistic persistence proofs to convince Schmid and Linford of the truth of the conclusions of those proofs by way of presentation of those proofs to Schmid and Linford (see 9–11). While I am sympathetic to this approach, other readers may wish to give a rather different characterization of the proper context for discussion of classical theistic persistence proofs.
Overall, I think that this is an impressive and interesting book. There are a number of infelicities, including some problems with the typesetting and the editing. There is also a sub-standard discussion of some comments about the validity of Aquinas's First Way that I made in Arguing about Gods (see 18–19 of the work under review). But these are very minor complaints. The work makes a significant contribution to our understanding of existential inertia and the role that appeals to existential inertia can play in response to classical theistic persistence proofs. (One thing that I haven't yet managed to work into this review, but about which I should say something, is the examination of the bearing of relatively recent physical theories – relativity and quantum mechanics – on the metaphysical topics under discussion. In particular, Schmid and Linford have interesting things to say about the ways in which considerations about atemporal wave-function monism magnify the ‘gap’ problem, and about ways in which considerations about relativity bear on questions about presentism and related philosophies of time.)
