I'm going to list and summarize what I deem to be the best arguments for God, as well as the major objections (such as they are) to God.
I. Framing the issue
It's important to have reasonable expectations regarding evidence for God. If the God of classical theism exists, then he's not directly detectable. God is not an empirical object. God is imperceptible to the five senses. The public evidence for God involves inferring God's existence from his effects and or his explanatory power.
That's not an unusual concept. For instance, the past is not directly detectable. At present, the past is imperceptible to the five senses. In some cases we have audio and visual records of the past. Even that's one step removed from the object. In most other cases, we infer the past from trace evidence. We infer the past from the residual effect of the past on the present. Likewise, we may infer abstract objects (e.g. numbers, possible worlds) based on their indispensable explanatory value. So the kinds of evidence for God are not unique to classical theism. There are analogous topics where we resort to the same kinds of evidence.
To take a specific example, interpreting a murder scene is an exercise in historical reconstruction. A homicide detective may have to determine the cause of death. Was it natural causes? Was it accidental? Or was it murder? A clever killer will attempt to conceal the true cause. A homicide detective must be alert to subtle clues of intelligent agency.
Of course, God is able to make his existence more explicit via an audible voice or miracles. Indeed, many people say they've witnessed that. But that's by no means a universal experience.
II. Philosophical/scientific arguments
These tend to be technical arguments that may be inaccessible to people without the aptitude or training. But that's not unique to theistic proofs. Presenting a formal argument for the existence of just about anything, including things we take for granted, may get us into deep waters. Even obvious truths can be hard to prove. Take proving the existence of an external world, or the reality of time.
1. Transcendental argument
Definition: Transcendental arguments are partly non-empirical, often anti-skeptical arguments focusing on necessary enabling conditions either of coherent experience or the possession or employment of some kind of knowledge or cognitive ability, where the opponent is not in a position to question the fact of this experience, knowledge, or cognitive ability, and where the revealed preconditions include what the opponent questions. Such arguments take as a premise some obvious fact about our mental life—such as some aspect of our knowledge, our experience, our beliefs, or our cognitive abilities—and add a claim that some other state of affairs is a necessary condition of the first one. Transcendental arguments most commonly have been deployed against a position denying the knowability of some extra-mental proposition, such as the existence of other minds or a material world. Thus these arguments characteristically center on a claim that, for some extra-mental proposition P, the indisputable truth of some general proposition Q about our mental life requires that P.Definition: As standardly conceived, transcendental arguments are taken to be distinctive in involving a certain sort of claim, namely that X is a necessary condition for the possibility of Y—where then, given that Y is the case, it logically follows that X must be the case too. Moreover, because these arguments are generally used to respond to skeptics who take our knowledge claims to be problematic, the Y in question is then normally taken to be some fact about us or our mental life which the skeptic can be expected to accept without question (e.g., that we have experiences, or make certain judgements, or perform certain actions, or have certain capacities, and so on), where X is then something the skeptic doubts or denies (e.g., the existence of the external world, or of the necessary causal relation between events, or of other minds, or the force of moral reasons).
Here's a limitation:
Because of their anti-skeptical ambitions, transcendental arguments must begin from a starting point that the skeptic can be expected to accept, the necessary condition of which is then said to be something that the skeptic doubts or denies. This will then mean that such arguments are ineffective against very radical forms of skepticism, which doubt the laws of logic, and/or which refuse to accept any starting point as uncontentious; and it will also mean that they may be effective against a skeptic who is prepared to accept some starting point, but then ineffective against another skeptic who is not.
However, that's not necessarily a weakness of transcendental arguments. Rather, it may expose how unreasonable the skeptic is.
Here are some examples of what I'd classify as theistic transcendental arguments:
i) Argument from abstract objects:
ii) Argument from knowledge
iii) Evolutionary argument against naturalism
iv) Argument from truth
I think this is a promising, and potentially powerful argument, but it's underdeveloped. Here's the seminal argument:
Even if there were no human intellects, there could be truths because of their relation to the divine intellectual. But if, per impossible, there were no intellects at all, but things continued to exist, then there would be no such reality as truth. Aquinas, De Veritate.
One way to unpack this is to show that truths are true beliefs or concepts. Beliefs and concepts are mental entities. If so, truth can't exist apart from minds.
According to atheism, this would be mean there were no truths before there were minds to think them. That, however, seems to be profoundly counterintuitive. On that view, it wasn't true that the moon orbits the earth until humans evolved to the point where they could entertain that belief.
2. Teleological argument
i) The fine-tuning argument
Summary: These are the fundamental constants and quantities of the universe. Each of these numbers have been carefully dialed to an astonishingly precise value - a value that falls within an exceedingly narrow, life-permitting range. If any one of these numbers were altered by even a hair's breadth, no physical, interactive life of any kind could exist anywhere. There'd be no stars, no life, no planets, no chemistry…The fact is our universe permits physical, interactive life only because these, and many other numbers, have been independently and exquisitely balanced on a razor's edge…The probabilities involved are so ridiculously remote as to put the fine-tuning well beyond the reach of chance.
Guillermo Gonzalez & Jay W. Richards. The Privileged Planet: How Our Place in the Cosmos Is Designed for Discovery (Regnery, 2004).
A potential weakness of the fine-tuning argument is its relative dependence on the shifting sands of modern physics and cosmology. However, some of the data feeding into the fine-tuning argument are well-established.
ii) Argument from irreducible complexity
Definition: A functional system is irreducibly complex if it contains a multipart subsystem (i.e., a set of two or more interrelated parts) that cannot be simplified without destroying the system’s basic function. I refer to this multipart subsystem as the system’s irreducible core.3 This definition is more subtle than it might first appear, so let’s consider it closely. Irreducibly complex systems belong to the broader class of functionally integrated systems. A functionally integrated system consists of parts that are tightly adapted to each other and thus render the system’s function highly sensitive to isolated changes of those parts. For an integrated system, a change in one place often shuts down the system entirely or else requires multiple changes elsewhere for the system to continue to function. We can therefore define the core of a functionally integrated system as those parts that are indispensable to the system’s basic function: remove parts of the core, and you can’t recover the system’s basic function from the other remaining parts. To say that a core is irreducible is then to say that no other systems with substantially simpler cores can perform the system’s basic function.
iii) Argument from specified complexity
Definition/summary: What is specified complexity? Recall the novel Contact by Carl Sagan (1985). In that novel, radio astronomers discover a long sequence of prime numbers from outer space. Because the sequence is long, it is complex. Moreover, because the sequence is mathematically significant, it can be characterized independently of the physical processes that bring it about. As a consequence, it is also specified. Thus, when the radio astronomers in Contact observe specified complexity in this sequence of numbers, they have convincing evidence of extraterrestrial intelligence. Granted, real-life SETI researchers have thus far failed to detect designed signals from outer space. The point to note, however, is that Sagan based the SETI researchers’ methods of design detection on actual scientific practice. To employ specified complexity to detect design is to engage in effect-to-cause reasoning. As a matter of basic human rationality, we reason from causes to effects as well as from effects back to causes. Scientific experimentation, for instance, requires observation and the control of variables, and thus typically employs cause-to-effect reasoning: the experimenter, in setting up certain causal processes in an experiment, constrains the outcome of those processes (the effect). But, in many cases, we do not have control of the relevant causal processes. Rather, we are confronted with an effect and must reconstruct its cause. Thus, an alien visiting Earth and confronted with Mt. Rushmore would need to figure out whether wind and erosion could produce it or whether some additional factors might be required. To sum up, many special sciences already employ specified complexity as a sign of intelligence—notably forensic science, cryptography, random number generation, archeology, and the search for extraterrestrial intelligence (Dembski 1998, chs. 1 and 2). Design theorists take these methods and apply them to naturally occurring systems (see Dembski and Ruse 2004, pt IV). When they do, these same methods for identifying intelligence indicate that the delicate balance of cosmological constants (known as cosmological fine-tuning) and the machine-like qualities of certain tightly integrated biochemical systems (known as irreducibly complex molecular machines) are the result of intelligence and highly unlikely to have come about by purely material forces (like the Darwinian mechanism of natural selection and random variation). For such design-theoretic arguments at the level of cosmology, see Gonzalez and Richards (2004); for such design-theoretic arguments at the level of biology, see Behe (1996). In any event, it is very much a live possibility that design in cosmology and biology is scientifically detectable, thus placing intelligent design squarely within the realm of science.
3. Cosmological argument
i) I think the best cosmological argument is a version of the Leibnizian cosmological argument. That argument is partly a posteriori, inasmuch as it appeals to the universe–and partly a priori, inasmuch as it appeals to a metaphysical principle (i.e. the distinction between contingency and necessity). A potential advantage it has over some scientific theistic proofs is that it's less wedded to the particulars of modern physics and cosmology. It operates at a more general level. Even if the universe had no beginning, in principle you could still mount a successful Leibnizian cosmological argument. Even if current theories in modern physics and cosmology undergo radical revision, that doesn't affect the Leibnizian cosmological argument. Here's a sophisticated example:
ii) William Lane Craig has popularized the kalam cosmological argument. That argument is partly a posteriori, inasmuch as it appeals to the temporality of the universe–and partly a priori inasmuch as it appeals to a metaphysical principle (the alleged impossibility of an actual temporal infinite or the impossibility of traversing an actual temporal infinite). If successful, an advantage of this argument is that it's not dependent on the particulars and vicissitudes of modern physics and cosmology. It's an essentially metaphysical argument, based on the alleged impossibility of an actual commutative temporal infinite. A potential vulnerability of the argument is dependence on the A-theory of time. So the proponent of this argument must first defend the A-theory of time, as a necessary presupposition of his argument, before he can turn to the cosmological argument proper.
iii) Two more philosophical arguments for God:
4. Modal ontological argument
Summary: If it's possible that a necessary being exists, then he exists in at least one possible world. But if he's a necessary Being, then he exists in every possible world (since that's how necessity is defined in modal metaphysics). If he necessarily exists in any world, then he necessarily exists in every world.
i) If it's possible for God to exist, then necessarily, God exists
ii) It's possible for God to exist.
iii) Therefore, necessarily, God exists
The challenge is to demonstrate the possibility of a necessary Being. That depends in part on the burden of proof. A critic needs to explain what is there about the concept of a necessary being that's impossible.
I think modal ontological arguments are promising. But a rigorous formulation can devolve into daunting technicalities and fine-grained modal intuitions.
5. Argument from reason
Summary: The necessary conditions of logical and mathematical reasoning, which undergird the human practice of science, require the rejection of all broadly materialistic worldviews.
6. Argument from consciousness
Summary: The existence of finite, irreducible consciousness (or its regular, lawlike correlation with physical states) provides evidence (with a strength I characterize) for the existence of God. The proponent must first argue for the irreducibility of consciousness, as a necessary presupposition of his argument. If he acquits that preliminary move, he then argues that “If irreducible consciousness exists (or is regularly correlated with physical states), then this provides evidence (to a degree specified in chapter two) for God’s existence.”
J. P. Moreland, Consciousness and the Existence of God: A Theistic Argument (Routledge, 2008).
III. Popular arguments
By popular, I mean arguments or evidence more accessible to nonspecialists. But that doesn't mean these are inferior to philosophical/scientific theistic proofs.
1. Argument from religious experience
There are specific examples. For instance:
i) Argument from answered prayer (or special providence):
That's something many Christians experience firsthand. It is, of course, important to distinguish between coincidence and divine intercession. Many examples of answered prayer (or special providence) should be classified as coincidence miracles. Although they may be the end-result of a natural chain of events, the outcome is too discriminating, opportune, timely, and unlikely to be a matter of chance.
ii) Argument from miracles
Except for the Resurrection, the argument from miracles is neglected in modern apologetics. Although Christian philosophers devote great attention to the subject of miracles, they typically defend the concept, possibility, and the credibility of miracles, rather than presenting evidence for actual miracles.
John Earman, Hume’s Abject Failure: The Argument Against Miracles (Oxford, 2000)
D. Geivett & G. Habermas, eds., In Defense of Miracles: A Comprehensive Case for God's Action in History (IVP, 1997)
Joseph Houston, Reported Miracles: A Critique of Hume (Cambridge, 1994)
David Johnson, Hume, Holism, and Miracles (Cornell, 2002)
Peter vanInwagen: http://andrewmbailey.com/pvi/Of_Of_Miracles.pdf
Peter vanInwagen: http://andrewmbailey.com/pvi/Of_Of_Miracles.pdf
Craig Keener, Miracles: The Credibility of the New Testament Accounts, 2 vols. (Baker, 2011)
Rex Gardner, Healing Miracles: A Doctor Investigates (Darton, Longman & Todd Ltd, 1986)
Keener also has a number of YouTube presentations on miracles.
Two monographs combining a philosophical defense with case studies:
Robert Larmer, The Legitimacy of Miracle (Lexington Books, 2013)
Robert Larmer, Dialogues on Miracle (Wipf & Stock, 2015)
2. Argument from prophecy
T. D. Alexander, The Servant King: The Bible's Portrait of the Messiah (Regent College Publishing, 2003)
Herbert Bateman et al. Jesus the Messiah: Tracing the Promises, Expectations, and Coming of Israel's King(Kregel, 2012)
J. Alec Motyer, Look to the Rock: An Old Testament Background to Our Understanding of Christ (Kregel Academic & Professional; 1st ed., 2004)
O. Palmer Robertson, The Christ of the Prophets (P & R Publishing, 2008)
Michael Rydelnik’s The Messianic Hope: Is the Hebrew Bible Really Messianic? (B& H 2010)
John H. Sailhamer, The Meaning of the Pentateuch: Revelation, Composition and Interpretation (IVP, 2009)
3. Moral argument
4. Existential argument
This goes to the question of whether atheism entails moral and/or existential nihilism. For instance:
5. The Bible
If the Bible is even approximately true, then that not only proves mere theism, but is one-stop shopping for Christian theism. There are many books expounding the general historical reliability of Scripture, as well as the historical Jesus in particular. For instance:
Paul Barnett, Finding the Historical Jesus (Eerdmans, 2009)
Richard Bauckham, Jesus and the Eyewitnesses (Eerdmans, 2nd ed., 2017)
Daniel Block, et al. eds. Israel: Ancient Kingdom or Late Invention? (B&H Academic, 2008)
Craig Blomberg, The Historical Reliability of the New Testament (B&H Academic, 2016)
D. A. Carson, ed. The Enduring Authority of the Christian Scriptures (Eerdmans, 2016)
S. Cowan & T. Wilder. In Defense of the Bible: A Comprehensive Apologetic for the Authority of Scripture (B&H, 2013)
Paul Rhodes Eddy & Gregory Boyd, The Jesus Legend: A Case for the Historical Reliability of the Synoptic Jesus Tradition (Baker, 2007)
Craig A. Evans, Jesus and His World: The Archeological Evidence (WJK, 2012)
Colin Hemer, The Book of Acts in the Setting of Hellenistic History (Eisenbrauns, 1990)
R. Hess, et al. eds. Critical Issues in Early Israelite History (Eisenbrauns, 2008)
James Hoffmeier. The Archaeology of the Bible (Lion Hudson, 2008)
James Hoffmeier, Israel in Egypt: Evidence for the Authenticity of the Exodus Tradition (Oxford, 1997)
James Hoffmeier, Ancient Israel in Sinai: The Evidence for the Authticity of the Wilderness Tradition (Oxford, 2005)
James Hoffmeier & Dennis MaGary, eds., Do Historical Matters Matter to Faith? (Crossway, 2012)
James Hoffmeier & Alan Millard, eds. The Future of Biblical Archaeology: Reassessing Methodologies and Assumptions (Eerdmans, 2004)
V. Philips Long et al. eds. Windows into Old Testament History: Evidence, Argument, and the Crisis of "Biblical Israel" (Eerdmans, 2002)
Craig Keener, Acts: A Exegetical Commentary, 4 vols. (Baker Academic, 2012-2015)
Craig Keener, The Historical Jesus of the Gospels (Eerdmans, 2009)
Kenneth Kitchen, On the Reliability of the Old Testament (Eerdmans 2003)
Lydia McGrew, Hidden in Plain View: Undesigned Coincidences in the Gospels and Acts (DeWard, 2017)
Alan Millard et al. eds. Faith, Tradition, and History: Old Testament Historiography in Its Near Eastern Context(Eisenbrauns, 1994)
Stanley Porter, John, His Gospel, and Jesus (Eerdmans, 2016)
Vern Poythress, Inerrancy and the Gospels (Crossway 2012)
I. Provan, et al. A Biblical History of Israel (WJK, 2nd ed., 2015)
Andrew Steinmann. From Abraham to Paul: A Biblical Chronology (Concordia, 2011)
Bruce. W. Winter, The Book of Acts in Its First Century Setting, vols. 1-4 (Eerdmans)
1. Critiquing theistic proofs
Atheists spend lots of time attacking theistic proofs. I don't have much to say about that in this post. For one reason, Christians who formulate arguments for God generally take atheist objections into account.
2. God of the gaps
Atheists routinely attack scientific arguments for God as an argument from ignorance. But we should operate with presumptive naturalism because methodological atheism has a great track record of filling gaps.
There are, however, multiple problems with that objection:
i) It substitutes naturalism of the gaps for God of the gaps.
ii) It misconceives Christian theology. God doesn't directly cause every event–or even most evens. Rather, there's a doctrine of general providence, where natural events are normally the result of physical causes. Therefore, the fact that science discovers natural mechanisms doesn't fill gaps that were previously the provenance of God's immediate fiat. Folk religion may be guilty of that, but not Christian theology.
iii) In addition, the objection sometimes begs the question. For instance, an atheist will say people use to attribute mental illness to demonic possession, but we now know mental illness has natural causes.
However, to assert that demonic possession is inherently superstitious and unscientific not only begs the question, but ignores evidence to the contrary. For instance:
M. Scott Peck, Glimpses of the Devil A Psychiatrist's Personal Accounts of Possession, Exorcism , and Redemption (Free Press, 2009)
iii) Design arguments are arguments from knowledge. Indications of rational agency. To take a comparison, a detective may have to determine whether a death was accidental or homicidal. A clever killer will stage a murder to make it appear to be accidental death, or death by natural causes. Yet there may be subtle indications that it was murder. Imagine an atheist objecting on the grounds that we should always be patient and assume death was accidental or due to natural causes. Even if we can't explain it that way, we should wait until we develop a theory to do so. To invoke a personal agent (murderer) is homicide of the gaps.
iii) Some issues, like the hard problem of consciousness, arguably belong to a different domain than physicalism. Arguments for the irreducibility of consciousness are metaphysical rather than scientific.
3. God-talk is meaningless
Although it has few followers today, there was a time when some atheists (e.g. Antony Flew, Kai Nielsen) said God-talk is meaningless. Sometimes dubbed theological noncognitivism.
Nielsen argued that anthropomorphic descriptions of God are meaningful, but false. By contrast, classical theism is meaningless. That, however, assumes that certain divine attributes like timelessness and spacelessness lack positive content. But if the notion of a timeless and/or spaceless entity is meaningless, then the notion of abstract objects (e.g. numbers, possible worlds) is meaningless. Yet that's a radical claim. Even philosophers who deny the existence of abstract objects don't necessary contend that the notion is meaningless, just unnecessary. Likewise, it's arguable that mental entities are spaceless. But we have direct experience of what mental entities are.
4. Presumption of atheism
Some atheists (e.g. Antony Flew) contend that the onus is on the person making the assertion–in this case, the theist. That, however, is deceptive. For a denial is no less a truth claim than an affirmation. To say there's no evidence for God, or insufficient evidence for God is itself an assertion. So both sides of the debate have a burden of proof.
5. Argument from evil
This is different from some atheistic arguments because it claims to be positive evidence for God's nonexistence, and not merely lack of evidence. However, the argument is beset by problems:
i) As William Dembski noted in his debate with Christopher Hitchens:
In establishing God’s goodness, let’s therefore first level the playing field. The sixth century Christian philosopher Boethius helps us here. In his Consolation of Philosophy, Boethius states the following paradox: “If God exists, whence evil? But whence good, if God does not exist?” Boethius contrasts the problem that evil poses for theism with the problem that good poses for atheism. The problem of good does not receive nearly as much attention as the problem evil, but it is the more basic problem. That’s because evil always presupposes a good that has been subverted.
Evil presumes a deviation from an ideal. But in a godless cosmos, devoid of teleology, how can anything be dysteleological?
ii) In principle, an atheist can reject moral realism but still claim that the problem of evil generates an inconsistent triad for Christian theism: If God is omniscient, omnipotent, and benevolent, how come evil occurs? You can either deny God's existence or relieve the dilemma by denying one of the conflicting attributes.
However, a problem with that formulation is that it's too abstract. Indeed, it's in tension with another atheist argument. Atheists routinely assert that the Biblical God is morally reprehensible, because he permits, commits, or commands evil. That, however, has the ironic consequence of disabling the argument from evil, for by their own admission, Yahweh's existence is consistent with evil. So Bible writers don't regard God's benevolence in the same atheists do.
6. The Euthyphro dilemma
Some atheists appeal to the Euthyphro dilemma to negate the possibility of Christian ethics. But there are problems with that move:
i) Secular ethicist Richard Joyce has argued that the so-called Euthyphro dilemma is a false dilemma:
Divine command theory may still be problematic, but not for that reason.
ii) Even if an atheists succeeded in showing that Christian ethics can't undergird moral realism, he hasn't shown that secular ethics is any more successful at undergirding moral realism. It may merely deflect attention away from intractable problems with secular ethics. Punting to real or alleged problems with Christian ethics doesn't mean you have a viable secular alternative.
If, moreover, an atheists concedes the futility of moral realism, then his attack on Christianity is a pyrrhic victory. What does that really accomplish? Like a sniper with terminal cancer: If I can't live, then I'll take everyone down with me!
If an atheist rejects moral realism, what's his rational incentive for attacking Christianity? Even if he thinks Christianity is false, he doesn't think it's morally wrong for people to be Christian.
iii) Even if the Euthyphro dilemma had bite, it only cuts into divine command theory. It doesn't cut into natural law theory.
7. Paradoxes of omniscience
Some atheists claim the notion of divine omniscience is paradoxical. However, Graham Oppy, who's the top atheist philosopher of his generation, is critical of the arguments deployed against omniscience:
8. Paradoxes of omnipotence
Some atheists claim the notion of divine omnipotence is paradoxical, viz. the stone paradox. However, these are specious antinomies, generated by wooden, arbitrary, a priori definitions of omnipotence. For instance:
9. You have other objections concerning divine hiddenness, divine freedom (William Rowe), mass extinction, and the argument from scale. Since I myself have addressed these objections on various occasions, I don't have anything new to say.