Kalam cosmological argument

The Kalam cosmological argument is a modern formulation of the cosmological argument for the existence of God. It is named after the Kalam (medieval Islamic scholasticism) from which many of its key ideas originated.^[1] Philosopher and theologian William Lane Craig was principally responsible for revitalizing these ideas for modern academic discourse through his book The Kalām Cosmological Argument (1979), as well as other publications.

The argument's central thesis is the metaphysical impossibility of a temporally past-infinite universe and of actual infinities existing in the real world, traced by Craig to 11th-century Persian Muslim scholastic philosopher Al-Ghazali. This feature distinguishes it from other cosmological arguments, such as that of Thomas Aquinas, which rests on the impossibility of a causally ordered infinite regress, and those of Leibniz and Samuel Clarke, which refer to the principle of sufficient reason.^[2]

Since Craig's original publication, the Kalam cosmological argument has elicited public debate between Craig and Graham Oppy, Adolf Grünbaum, J. L. Mackie and Quentin Smith, and has been used in Christian apologetics.^[3][4] According to Michael Martin, the cosmological arguments presented by Craig, Bruce Reichenbach, and Richard Swinburne are "among the most sophisticated and well-argued in contemporary theological philosophy".^[5]

The most prominent form of the Kalam cosmological argument, as defended by William Lane Craig, is expressed in two parts, as an initial syllogism followed by further philosophical analysis.^[6]

The Kalam cosmological argument is a deductive argument. Therefore, if both premises are true, the truth of the conclusion follows necessarily.

1. Everything that begins to exist has a cause.
2. The universe began to exist.
3. Therefore, the universe has a cause.

Craig argues that the cause of the universe necessarily embodies specific properties, in being:^[7]

• Uncaused, otherwise an infinite regress of causes would arise.
• Timeless (therefore changeless), spaceless, immaterial and enormously powerful, in creating spacetime and its contents ex nihilo.
• Personal, possessing non-deterministic agency, in creating the universe from a timeless state (without prior determining conditions).
• Singular, per Occam's razor, in the absence of good reasons to believe in the existence of more than one uncaused cause.

Based upon this, he appends a further premise and conclusion:^[7]

4. If the universe has a cause, then an uncaused, personal Creator of the universe exists who sans (without) the universe^[8] is beginningless, changeless, immaterial, timeless, spaceless and enormously powerful.
5. Therefore, an uncaused, personal Creator of the universe exists, who sans the universe is beginningless, changeless, immaterial, timeless, spaceless and enormously powerful.

Craig notes the theological implications that follow from the final conclusion of this argument.^[9]

The Kalam cosmological argument was influenced by the concept of the prime mover, introduced by Aristotle. It originates in the works of theologian and philosopher John Philoponus (490–570 AD)^[10] and was developed substantially under the medieval Islamic scholastic tradition during the Islamic Golden Age. Important historical proponents include Al-Kindi,^[11] Al-Ghazali^[12] and St. Bonaventure.^[13][14][15]

One of the earliest formulations of the argument is described by Islamic philosopher and theologian Al-Ghazali:^[16]

"Every being which begins has a cause for its beginning; now the world is a being which begins; therefore, it possesses a cause for its beginning."

The argument developed as a concept within Islamic theology between the 9th and 12th centuries, refined in the 11th century by Al-Ghazali (The Incoherence of the Philosophers) and in the 12th by Ibn Rushd (Averroes).^[17] It reached medieval Christian philosophy in the 13th century and was discussed by Bonaventure as well as Thomas Aquinas in his Summa Theologica (I, q.2, a.3) and Summa Contra Gentiles (I, 13).

Islamic perspectives may be divided into positive Aristotelian responses strongly supporting the argument, such as those by Al-Kindi and Averroes, and negative responses critical of it, including those by Al-Ghazali and Muhammad Iqbal.^[18] Al-Ghazali was unconvinced by the first-cause arguments of Al-Kindi, arguing that only the infinite per se (that is an essentially ordered infinite series) is impossible, arguing for the possibility of the infinite per accidens (that is an accidentally ordered infinite series). He writes:^[19]

"According to the hypothesis under consideration, it has been established that all the beings in the world have a cause. Now, let the cause itself have a cause, and the cause of the cause have yet another cause, and so on ad infinitum. It does not behove you to say that an infinite regress of causes is impossible."

Muhammad Iqbal also stated:^[18]

"A finite effect can give only a finite cause, or at most an infinite series of such causes. To finish the series at a certain point, and to elevate one member of the series to the dignity of an un-caused first cause, is to set at naught the very law of causation on which the whole argument proceeds."

According to atheist philosopher Quentin Smith, "a count of the articles in the philosophy journals shows that more articles have been published about Craig's defense of the Kalam argument than have been published about any other philosopher's contemporary formulation of an argument for God's existence."^[20]

The Kalam cosmological argument has received criticism from philosophers such as J. L. Mackie, Graham Oppy, Adolf Grunbaum, Michael Martin, Quentin Smith, Wes Morriston and Alex Malpass as well as physicists Sean M. Carroll, Lawrence Krauss and Victor Stenger.^[21]

Modern discourse encompasses the fields of both philosophy and science (e.g. the fields of quantum physics and cosmology), which Bruce Reichenbach summarises as:^[22]

"... whether there needs to be a cause of the first natural existent, whether something like the universe can be finite and yet not have a beginning, and the nature of infinities and their connection with reality".

Since the temporal ordering of events is central, the Kalam argument also brings issues of the nature of time into the discussion.^[23]

Craig and James Sinclair have stated that the first premise is obviously true, at the least more plausibly true than its negation.^[24] Craig offers three reasons to support the premise:^[25]

1. Rational intuition: The first premise is self-evidently true, being based upon the metaphysical intuition that "something cannot come into being from nothing" (Latin: ex nihilo nihil fit) originating from Parmenidean philosophy.
2. Reductio ad absurdum: If false, it would be inexplicable why just anything and everything does not randomly come into existence without a cause. To come into being without any cause is to come into being from nothing, which he says is surely absurd.
3. Inductive reasoning from both common experience and scientific evidence, which constantly verifies and never falsifies its truth.

According to Reichenbach, "the Causal Principle has been the subject of extended criticism", which can be divided into philosophical and scientific criticisms.^[26]

Graham Oppy, J. L. Mackie and Wes Morriston have objected to the intuitiveness of the first premise.^[27][28][29] Oppy states:

"Mackie, [Adolf] Grunbaum, [Quentin] Smith and I—among many others—have taken issue with the first premise: why should it be supposed that absolutely everything which begins to exist has a cause for its beginning to exist?"

Mackie affirms that there is no good reason to assume a priori that an uncaused beginning of all things is impossible. Moreover, that the Causal Principle cannot be extrapolated to the universe from inductive experience. He appeals to David Hume's thesis (An Enquiry Concerning Human Understanding) that effects without causes can be conceived in the mind, and that what is conceivable in the mind is possible in the real world.^[30] This argument has been criticised by Bruce Reichenbach and G.E.M. Anscombe, who point out the phenomenological and logical problems in inferring factual possibility from conceivability.^[31][32] Craig notes:^[33][34]

"Hume himself clearly believed in the causal principle. He presupposes throughout the Enquiry that events have causes, and in 1754 he wrote to John Stewart, 'But allow me to tell you that I never asserted so absurd a Proposition as that anything might arise without a cause'."

Morriston asserts that causal laws are physical processes for which we have intuitive knowledge in the context of events within time and space, but that such intuitions do not hold true for the beginning of time itself. He states:^[35]

"We have no experience of the origin of worlds to tell us that worlds don't come into existence like that. We don't even have experience of the coming into being of anything remotely analogous to the 'initial singularity' that figures in the Big Bang theory of the origin of the universe."

Craig responds that causal laws are unrestricted metaphysical truths that are "not contingent upon the properties, causal powers, and dispositions of the natural kinds of substances which happen to exist", remarking:^[36]

"The history of twentieth century astrophysical cosmology belies Morriston's claim that people have no strong intuitions about the need of a causal explanation of the origin of time and the universe."

For scientific evidence against the first premise, Paul Davies appeals to the phenomenon of quantum indeterminacy, wherein subatomic processes appear to contradict a deterministic model of cause and effect.^[37] Craig argues that, though quantum indeterminism uproots the proposition that "every event has a cause", it is nonetheless consistent with the causal premise that "everything that begins to exist has a cause", denoting the more modest view that objects cannot come into existence entirely devoid of causal conditions.^[38]

He also notes that the phenomenon of indeterminism is specific to the Copenhagen interpretation of quantum mechanics, pointing out that this is only one of a number of different interpretations, some of which he states are fully deterministic (mentioning David Bohm) and none of which are as yet known to be true. He concludes that subatomic physics is not a proven exception to the first premise.^[39]

Philosopher Quentin Smith refers to the example of virtual particles, which appear and disappear through fluctuations in the quantum vacuum, apparently at random, to assert the tenability of uncaused natural phenomena.^[40] In his book A Universe from Nothing: Why There is Something Rather Than Nothing, cosmologist Lawrence Krauss has proposed how quantum mechanics can explain how spacetime and matter can emerge from 'nothing' (referring to the quantum vacuum). Philosopher Michael Martin has also appealed to quantum vacuum fluctuation models to support the idea of a universe with uncaused beginnings. He writes:^[41]

"Even if the universe has a beginning in time, in the light of recently proposed cosmological theories this beginning may be uncaused. Despite Craig's claim that theories postulating that the universe 'could pop into existence uncaused' are incapable of 'sincere affirmation,' such similar theories are in fact being taken seriously by scientists."

Philosopher David Albert has criticised use of the term 'nothing' in describing the quantum vacuum. In a review of Krauss's book, he states:^[42]

"Relativistic-quantum-field-theoretical vacuum states—no less than giraffes or refrigerators or solar systems—are particular arrangements of elementary physical stuff. The true relativistic-quantum-field-theoretical equivalent to there not being any physical stuff at all isn't this or that particular arrangement of the fields—what it is (obviously, and ineluctably, and on the contrary) is the simple absence of the fields."

Craig argues that the quantum vacuum state, in containing measurable energy, cannot be characterised as nothing, therefore, that phenomena originating from the quantum vacuum cannot be described as uncaused. On the topic of virtual particles, he writes:^[43]

"For virtual particles do not literally come into existence spontaneously out of nothing. Rather the energy locked up in a vacuum fluctuates spontaneously in such a way as to convert into evanescent particles that return almost immediately to the vacuum."

Cosmologist Alexander Vilenkin has stated that even "the absence of space, time and matter" cannot truly be defined as 'nothing' given that the laws of physics are still present, though it would be "as close to nothing as you can get".^[44]

Craig defends premise two using both scientific and philosophical arguments for the finitude of the past, covering the topics of cosmology, physics and a philosophical examination of actual infinities.

For physical evidence, Craig appeals to:

1. Scientific confirmation against a past-infinite universe in the form of the second law of thermodynamics.^[45]
2. Scientific evidence that the universe began to exist a finite time ago at the Big Bang.^[45]
3. The Borde–Guth–Vilenkin theorem,^[46] a cosmological theorem which deduces that any universe that has, on average, been expanding throughout its history cannot have been expanding indefinitely in the past but must have a past boundary at which inflation began.

Professor Alexander Vilenkin, one of the authors of the Borde–Guth–Vilenkin theorem, writes:^[47]

"A remarkable thing about this theorem is its sweeping generality. We made no assumptions about the material content of the universe. We did not even assume that gravity is described by Einstein's equations. So, if Einstein's gravity requires some modification, our conclusion will still hold. The only assumption that we made was that the expansion rate of the universe never gets below some nonzero value, no matter how small."

According to Vilenkin and co-author Alan Guth, the past boundary described by the Borde–Guth–Vilenkin theorem does not necessarily represent a cosmic beginning, instead the beginning of cosmic inflation.^[48] Though it "opens the door" for theories other than an absolute beginning, in a 2012 lecture, Vilenkin would discuss problems with alternative theories that would claim to avoid a cosmological beginning (including eternal inflation, cyclic and emergent models) concluding: "All the evidence we have says that the universe had a beginning".^[49] In publications, he would propose that the Borde–Guth–Vilenkin theorem is sufficient evidence for a beginning of the universe.^[50][51][52]

Craig has stated that, if anything existed before the past boundary described by the theorem, it would be a non-classical region described by an as-yet-undetermined theory of quantum gravity. He refers to statements by Vilenkin^[53] that, in such a scenario the non-classical region, rather than the boundary, would then be the beginning of the universe. He concludes, "either way, the universe began to exist."^[54]

Victor J. Stenger has referred to the Aguirre–Gratton model^[55] for eternal inflation as an exemplar by which to avoid a cosmic beginning.^[56] In correspondence with Stenger, Vilenkin remarked how the Aguirre–Gratton model attempts to evade a beginning by reversing the "arrow of time" at t = 0, but that: "This makes the moment t = 0 rather special. I would say no less special than a true beginning of the universe."^[57]

For philosophical evidence of the finitude of the past, Craig refers to:

1. The Hilbert's Hotel thought experiment, as evidence of the metaphysical impossibility of actual infinites existing in reality.^[58]
2. Bertrand Russell's tale of Tristram Shandy, as evidence of the impossibility of forming an actual infinite by successive addition.^[59][60]

Accordingly, he argues:

1. A beginningless series of past events would represent an actual infinite existing in reality, which is metaphysically impossible.^[1]
2. Past events are a series formed by successive addition, which therefore cannot be extended to an infinite past.^[1][61]

Philosopher Andrew Loke similarly characterizes the metaphysical problems of a beginningless universe, referring to a variation of Hilbert's Hotel,^[62] and Ben Waters has published the story of Methuselah's Diary as a refinement of the tale of Tristram Shandy.^[63]

Craig maintains that, though it is metaphysically impossible for actual infinities to exist in the real world, they (and the absurdities that attend their existence in the real world) are describable via mathematics, therefore logically possible.^[64] He also distinguishes between actual infinities and potential infinities, stating that it is fully possible for potential infinites to exist in the real world, in contrast to the former:^[65]

"A potential infinite is a series which has a beginning and is growing indefinitely; infinity serves merely as an ideal limit of the series which it never reaches ... That’s impossible, since for any natural number n, n+1 is always a finite number."

Thomist philosopher Edward Feser has remarked that the Kalam argument is based upon a presentist theory of time in which past and future events do not exist, declaring that this would be incompatible with objections against an eternal past based upon Hilbert's Hotel:^[66]

"If the present alone is real, then how can an infinite series of events in time count as an actual infinite? Past moments of time are not actual; they no longer exist ... In the Hilbert’s hotel scenario [the rooms and guests] exist together all at once, at the same time."

Craig affirms that the simultaneous existence of the enumerated objects is irrelevant, so long as past events have been real, thus instantiated in reality, they can be counted.^[67][68] He refers to a narrative by Aquinas of a blacksmith who, from an eternal past, has used and broken successive hammers. He notes that the discarded hammers need no longer exist to be counted as an actual infinite.^[69] Furthermore, that the absurdities attending the existence of actual infinites in reality still apply if the enumerated objects no longer exist:^[70]

"... in an infinite series of past events, the number of odd-numbered events is the same as the number of all the events, even though the latter collection includes all the odd-numbered events plus an infinite number of even-numbered events as well."

Feser contends that past events are more analogous to abstract objects, such as natural numbers, than concrete objects, such as hotel rooms and guests. For this, he refers to Aristotle's postulate that denies the existence of time independent of objects that change:^[71]

"To speak of time apart from change is a bit like speaking of a universal like redness apart from actual red things—it is to engage in abstraction from the concrete conditions under which the thing in question (redness, or time) can actually exist."

Craig proposes that an endless future qualifies as a potential rather than actual infinite, given that future events, unlike past events, are yet to be actualised and merely potential.^[68] Morriston and Malpass argue that this asymmetry is arbitrary. They stipulate that an endless future should be deemed actually infinite, given that future events will be actual, just as past events are deemed actual in that they have been. They conclude that, if Hilbert's Hotel disproves an eternal past, so too does it negate an endless future, contradicting Christian theology.^[72]

Noting in agreement that future events cannot be actually infinite, Craig responds that this objection begs the question and fails to address the ontological distinction between past and future qualified by the objectivity of temporal becoming under presentism.^[73][74] He writes:

"The series of future events can be finite but endless. In such a case the series is potentially infinite. This is a view that is so widespread and commonly accepted in the history of philosophy and science that the objector has a considerable burden of proof to bear ..."

In a critique of Craig's book The Kalām Cosmological Argument, published in 1979, Michael Martin writes:^[75]

"It should be obvious that Craig's conclusion that a single personal agent created the universe is a non sequitur. At most, this Kalam argument shows that some personal agent or agents created the universe. Craig cannot validly conclude that a single agent is the creator. On the contrary, for all he shows, there may have been trillions of personal agents involved in the creation."

Martin adds that Craig has not justified his claim of creation ex nihilo, remarking that the universe may have been created from pre-existing material in a timeless or eternal state. Moreover, that Craig takes his argument too far beyond what his premises allow in stating that the creator is greater than the universe. For this, he cites the example of a parent "creating" a child who eventually becomes greater than he or she.^[76]

In the Blackwell Companion to Natural Theology, published in 2009, Craig and James Sinclair present a philosophical analysis of the properties of the cause of the universe, denoting that they follow by entailment from the initial syllogism of the Kalam cosmological argument:^[7]

1. The universe must originate ex nihilo in being without natural cause, because no natural explanation can be causally prior to the very existence of the natural world. Therefore, the cause of the universe is outside of space and time (timeless, therefore changeless, and spaceless) as well as immaterial and enormously powerful, in bringing spacetime and its contents into existence.
2. Even if positing a plurality of causes prior to the origin of the universe, the causal chain must terminate in a cause which is absolutely first and uncaused, otherwise an infinite regress of causes would arise, which Craig and Sinclair argue is impossible.
3. Occam's Razor maintains that unicity of the First Cause should be assumed in the absence of specific reasons to believe that there is more than one causeless cause.
4. Agent causation, or volitional action, is the only ontological condition in which an effect can arise in the absence of prior determining conditions. Therefore, only personal, free agency can account for the origin of a first temporal effect from a changeless cause.
5. There are two conceivable categories of objects with the potential to be uncaused, spaceless, timeless and immaterial:
   • Minds (in some conceptions of mind-body dualism) may be characterized as immaterial and spatially unextended, with the potential to be unembodied, timeless, changeless and beginningless.^[77]
   • Abstract objects, such as the set of natural numbers, may be described as non-spatial and non-temporal, but do not sit in causal relationships and are therefore causally ineffective.^[78]

Based upon analysis of the information above, Craig concludes:^[7]

"... an uncaused, personal Creator of the universe exists, who sans the universe^[8] is beginningless, changeless, immaterial, timeless, spaceless and enormously powerful."

He notes the theological implications of this union of properties:^[79]

"... our whole universe was caused to exist by something beyond it and greater than it. For it is no secret that one of the most important conceptions of what theists mean by 'God' is Creator of heaven and earth."

The Kalam cosmological argument is based on the A-theory of time, also known as the "tensed theory of time" or presentism, in which past and future events do not exist in reality (they have existed, or will exist, but do not exist now) and only the present exists.^[80] This is opposed to the B-theory of time, also known as the "tenseless theory of time" or eternalism, in which past, present and future events co-exist, the passage of time is an illusion of consciousness and there is no privilege to the present other than as a frame of reference.^[81] Craig explains:^[38]

"On a B-Theory of time, the universe does not in fact come into being or become actual at the Big Bang; it just exists tenselessly as a four-dimensional space-time block that is finitely extended in the earlier than direction. If time is tenseless, then the universe never really comes into being, and, therefore, the quest for a cause of its coming into being is misconceived."

Craig has defended the A-theory against objections from J. M. E. McTaggart and hybrid A–B theorists.^[82][83] He refers to the neo‐Lorentzian interpretation of the Special Theory of Relativity, which he contends has become tenable in light of recent findings in quantum mechanics concerning Bell's theorem.^[84] Similar to Einstein's original interpretation, the Lorentzian view describes a 3-dimensional universe existing through time, with objects in motion demonstrating time dilation and length contraction. However, these relativistic distortions occur relative to a privileged rest frame (an absolute frame of reference for the universe) rather than relative to each observer.^[85]

He writes that the Lorentzian interpretation, in postulating an absolute space and absolute time, resolves the fragmentation of reality that characterises Einsteinian relativity, in which observers in relative motion occupy different spaces and times. Importantly, Lorentz's view of time as dynamic, and distinct from space, renders it compatible with the A-theory conception of a tensed universe.^[86]

Philosopher Yuri Balashov asserts that both consensus and evidence support Minkowski's interpretation of relativity, which posits a 4D geometric universe inhabited by objects extended in time as well as space.^[87] In spurning the notion of a 3D universe existing in time, Minkowskian relativity rejects the A-theory, correlating instead with the B-theory conception of a tenseless spacetime. Balashov remarks:^[88]

"Despite the fact that presentism has the firm backing of common sense and eternalism revolts against it, eternalism is widely regarded as almost the default view in contemporary debates, and presentism as a highly problematic view."

Craig suggests that Balashov underestimates the challenge to Minkowskian relativity posed by recent findings.^[85] He criticises Balashov for adopting a verificationist methodology that ignores important metaphysical and theological arguments underpinning the A-theory, affirming that correct interpretation of Special Relativity is not merely a physical, but also a metaphysical question.^[86][89]

In a 2020 interview, Craig proposed that the Kalam cosmological argument could be adapted to the B-theory of time by:^[90]

1. Abandoning the metaphysical argument against forming an actual infinity by successive addition.
2. Modifying the causal premise (replacing its appeal to the concept of 'coming into being' with the concept of 'beginning to exist').

Under the B-theory, scientific evidence for the finitude of the past would still be valid and the argument as a whole, though damaged and requiring reformulation, would still be tenable. Philosopher Ben Waters has also argued that a defense of the Kalam cosmological argument does not require a commitment to the A-theory.^[91]

• Craig, William Lane (1979). The Kalām Cosmological Argument. Wipf & Stock Publishers. ISBN 978-1-57910-438-2.
• Craig, William Lane (1994). Reasonable Faith. Moody Press. ISBN 978-0-89107-764-0.
• Craig, William Lane (2000). The Kalam Cosmological Argument. Wipf and Stock Publishers. ISBN 978-1-57910-438-2.
• Craig, William Lane (2001). Time and Eternity: Exploring God's Relationship to Time. Crossway. ISBN 978-1-58134-241-3.
• Craig, William Lane (2001b). God, Time, and Eternity, The Coherence of Theism II: Eternity. Springer. ISBN 978-1-4020-0011-9.
• Craig, William Lane (2001c). Time and the Metaphysics of Relativity. Springer. ISBN 978-0-521-52967-9.
• Craig, William Lane; Moreland, JP (2009). The Blackwell Companion to Natural Theology. John Wiley and Sons. ISBN 978-1-4051-7657-6.
• Mackie, J. L. (1982). The Miracle of Theism: Arguments For and Against the Existence of God. Oxford University Press. ISBN 978-0-19-824682-4.
• Martin, Michael (1990). Atheism: A Philosophical Justification. Temple University Press. ISBN 978-0-87722-943-8.
• Reichenbach, Bruce (2004). "Cosmological Argument: The Causal Principle and Quantum Physics". The Stanford Encyclopedia of Philosophy. Retrieved 10 September 2016.
• Smith, Quentin (2007). Martin, Michael (ed.). Kalam Cosmological Arguments for Atheism. Cambridge University Press.
• Waters, B. V. (2015). "Toward a new kalām cosmological argument". Cogent Arts and Humanities. 2 (1): 1–8. doi:10.1080/23311983.2015.1062461.
• Loke, Andrew Ter Ern (2017). God and Ultimate Origins. Springer International. ISBN 9783319575476.

• Moreland, J. P. (1987). Scaling the Secular City: A Defence of Christianity. Baker Academic.
• Craig, William Lane; Smith, Quentin (1993). Theism, Atheism, and Big Bang Cosmology. Clarendon. ISBN 978-0-19-826348-7.
• Craig, William Lane (1996). "Initial Arguments: A Defense of the Cosmological Argument for the Existence of God". Leadership University.
• Copan, Paul; Craig, William Lane (2004). Creation out of Nothing: A Biblical, Philosophical, and Scientific Exploration. Baker Academic.
• Vaas, Rüdiger (2004). "Time before Time – Classifications of universes in contemporary cosmology, and how to avoid the antinomy of the beginning and eternity of the world". Bilder aus der Wissenschaft. 10: 32–41. arXiv:physics/0408111. Bibcode:2004physics...8111V.
• Craig, William Lane (2007). "Causal Premiss of the Kalam Argument". Reasonable Faith. Retrieved 25 September 2024.
• Nowacki, Mark (2007). The Kalam Cosmological Argument for God. Studies in Analytic Philosophy. Prometheus Books. ISBN 978-1-59102-473-6.
• Craig, William Lane (2008). Reasonable Faith. Crossway Books. ISBN 978-1-4335-0115-9.