Cosmological
Kalam – Scientific and Philosophical
(P1) Whatever begins to exist has a cause. This premise expresses a basic metaphysical principle: things do not simply pop into existence from nothing, without a cause. (1) To deny (P1) is to say that something can come from absolutely nothing. - "Nothing" is not a kind of something; it has no properties, no potentialities, and no causal powers. - If things could arise from nothing without a cause, there is no reason why anything and everything would not appear uncaused at any time. (2) Everyday experience and scientific practice presuppose causal regularity. - Science is built on the assumption that events have explanations...that there are causes and laws to be discovered. - No scientist treats a macroscopic object's sudden appearance from nothing as a normal, explanation-free occurrence. (3) Quantum mechanics does not refute the causal principle. - So-called "quantum fluctuations" occur in a rich physical reality: fields, laws, and a quantum vacuum with structure. - They are not events arising from absolute nothingness; they are described by precise equations and boundary conditions. (4) The alternative is more incredible than the premise. - Believing that a universe can appear uncaused from literally nothing is, as Craig notes, "worse than magic." At least in magic there is a magician and a hat; on this view there is not even that. Therefore, it is far more rational to affirm that whatever begins to exist has a cause than to deny this deeply rooted causal principle.
(P2) The universe began to exist. Scientific Argument: Modern evidence strongly supports a cosmic beginning. (1) The Second Law of Thermodynamics. - The universe is running down: usable energy is being irreversibly converted into unusable forms. - If the universe had existed for an infinite time in the past, it should already have reached "heat death" (maximum entropy) long ago. - The fact that the universe is still in a low-entropy, life-permitting state strongly implies a finite past. (2) The expansion of the universe. - General relativity (Einstein, 1915) allowed cosmologists to model the large-scale structure and history of the universe. - Solutions to Einstein's equations (Friedmann, Lemaître) predicted an expanding universe. - Hubble's observations (1920s) of the redshift of distant galaxies empirically confirmed cosmic expansion. - Run the expansion backwards, and the distances between all points shrink toward a state of arbitrarily high density...a beginning of the universe. (3) The Borde–Guth–Vilenkin (BGV) theorem. - Borde, Guth, and Vilenkin (2003) proved that any universe which has, on average, been expanding throughout its history cannot be past-eternal, but must have a past boundary. - This applies not only to standard Big Bang cosmology but also to a wide range of inflationary and multiverse models. - As Vilenkin remarks: "All the evidence we have says that the universe had a beginning." (4) Failed attempts to avoid a beginning. - Steady-state, oscillating, and certain cyclic models have faced serious theoretical and observational problems. - Contemporary cosmology has largely given up the hope of a simple, past-eternal model that fits the data and escapes the BGV-type results. Taken together, thermodynamics, cosmic expansion, and modern cosmology provide strong evidence that the universe began to exist a finite time ago. See also: • Natural Theology: Cosmic Fine-Tuning
(P3) The universe began to exist. Philosophical Argument: Impossibility of an infinite regress of past events. (1) Actual infinites lead to absurdities in the real world. - An "actual infinite" is a completed totality with infinitely many members (not just a process that could keep going). - Hilbert's Hotel (Craig's standard illustration) shows the paradoxes of an actually infinite number of concrete things: • A hotel with infinitely many occupied rooms can still take infinitely many new guests while never becoming "full." • Subtracting equal finite quantities from the same infinite set yields contradictory results (e.g., ∞ − ∞ can give different answers). - These paradoxes suggest that an actual infinite collection of concrete objects cannot exist in reality; infinities belong in mathematics, not in the structure of the physical past. (2) An infinite temporal regress cannot be traversed. - The present moment has been reached. - If the number of prior events were actually infinite, it would be impossible to "traverse" an infinite sequence event by event to arrive at now. - No matter how far back you go, there would always be infinitely many events still left to occur before reaching the present, which is absurd. (3) The difference between a potential and an actual infinite. - A "potential infinite" (like counting numbers) can always be extended but is never complete. - The past, if it is real and completed, would be an actual infinite collection of completed events, not a mere potential infinite. - The philosophical problems attach to actual infinites of concrete things, which is exactly what an eternal past would require. (4) Therefore, the past cannot be infinite. - The philosophical arguments reinforce what the scientific evidence already indicates: the series of past events must have a beginning. See also: • Natural Theology: Contingency Argument
(C1) If whatever begins to exist has a cause (P1), and the universe began to exist (P2–P3), then the universe has a cause beyond itself. (1) The Kalam syllogism: - (P1) Whatever begins to exist has a cause. - (P2) The universe began to exist. - (C1) Therefore, the universe has a cause. (2) The universe cannot be the cause of itself. - For the universe to cause itself, it would have to exist before it existed, which is incoherent. - The cause must be "outside" or beyond the totality of space, time, matter, and energy that makes up the universe. (3) The causal principle applies to the beginning of the universe. - The claim is not that "every event inside the universe" has a cause and then we illegitimately extend this to the universe itself. - Rather, we apply the metaphysical principle directly: anything that begins to exist...whether inside or beyond the universe...requires a cause. Thus, from (P1) and (P2–P3), it logically follows that the universe has a transcendent cause.
(P5) The cause of the universe must be timeless (without the universe), spaceless, immaterial, enormously powerful, and plausibly personal. (1) Timeless and spaceless. - Space and time themselves begin at the origin of the universe on standard cosmology. - Therefore, the cause of the universe cannot be located in space and time; it must be beyond them. (2) Immaterial and non-physical. - Physical reality (matter/energy and fields) begins with the universe. - The cause cannot be another physical system inside the same space-time; it must be non-physical...an immaterial reality. (3) Enormously powerful. - The cause produces all matter, energy, space, and time from non-being (no pre-existing material). - Whatever has this kind of creative causal power is unimaginably powerful. (4) Plausibly personal (agent cause). - A timeless, changeless cause producing a temporal effect (the universe) suggests a free, personal choice rather than a mechanically necessary, impersonal process. - If the cause were a timeless, impersonal set of conditions, then its effect (the universe) would be timelessly present as well; it would not "begin" at a finite time. - By contrast, a personal agent can freely choose to bring about a new effect without prior determining conditions, explaining why the universe has a temporal beginning. (5) Only two kinds of candidates fit: abstract objects or an unembodied mind. - Abstract objects (like numbers) are causally inert; they do not cause anything. - The remaining live option for a timeless, spaceless, immaterial, powerful cause is something like a mind, a personal agent. Therefore, the cause of the universe is best understood as a powerful, immaterial, timeless, spaceless, personal Creator...what classical theism calls God.
(C2) Therefore, on the combined scientific and philosophical evidence, the best explanation of the universe's beginning is that it was caused to exist by a transcendent, timeless, spaceless, immaterial, enormously powerful, personal Creator...God.
Leibniz’ Contingency Argument
(P1) Everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause. This premise is a version of the principle of sufficient reason: reality is not a collection of utterly brute facts with no explanation at all. (1) Two basic types of explanation. - Necessary existence: Some things, if they exist, exist by the necessity of their own nature. It is impossible for them not to exist. - Contingent existence: Other things exist, but they could have failed to exist; they depend on something outside themselves. (2) Many philosophers and mathematicians regard abstract objects (numbers, sets) as necessary beings. - If such entities exist, they are not caused by anything else; they exist by their own nature. - Their explanation lies in their necessity, not in a prior cause. (3) Ordinary objects clearly exist contingently. - You, your parents, the earth, stars, and galaxies: none had to exist. - They came into existence and could have failed to exist; their existence calls for an external explanation. (4) “Just there, and that’s all” is not a genuine alternative. - If we found a sphere in the woods, we would naturally seek an explanation for it. - Increasing the size of the sphere (to a house, planet, or even the whole universe) does not remove the need for an explanation. - Our explanatory practices and rational intuitions strongly favor the idea that existing things have explanations. Therefore, it is reasonable to affirm that everything that exists has an explanation...either in the necessity of its own nature or in some external cause.
(P2) The universe is a contingent reality: it does not exist by a necessity of its own nature. (1) The universe is the totality of space-time, matter, and energy. - “Universe” here means all physical reality: all space, all time, all matter and energy, and the laws that govern them. (2) The universe could have been otherwise, or not existed at all. - It is logically possible that there be no physical universe. - It is also possible that the universe have different laws, constants, particle content, and initial conditions. - What is logically or metaphysically contingent does not exist by a necessity of its own nature. (3) Scientific evidence suggests physical reality had a beginning and specific initial conditions. - Modern cosmology (e.g., Big Bang, BGV theorem) points to a cosmic beginning and finely conditioned initial state. - A beginning and fine-tuned parameters fit better with contingency than with metaphysical necessity. (4) Our best modal intuitions treat the universe as contingent. - We can coherently conceive of different physical worlds or of no physical world at all. - Nothing in the nature of quarks, fields, or spacetime geometry demands that “this universe, exactly as it is” must exist. Therefore, the universe does not exist by the necessity of its own nature; it is a contingent reality.
(P3) If the universe has an explanation of its existence, that explanation is a necessary, non-physical, eternal, immaterial cause...what we call God. (1) The explanation of a contingent universe cannot be another contingent physical totality. - The universe is defined as the whole of space-time and physical reality. - Its explanation therefore cannot be some further physical thing “outside” it; any such thing would simply be part of the same totality. (2) The cause must be beyond space and time. - Space and time are part of the universe; the cause of the universe’s existence must be independent of them. - So the explanation of the universe must be non-spatial, non-temporal (timeless or eternal in the relevant sense). (3) The cause must be non-physical and immaterial. - Physical reality is exactly what is being explained. - Thus, the ultimate explanation cannot be another physical system; it must be non-physical and immaterial. (4) The cause must be metaphysically necessary. - Since the universe is contingent, its explanation...per (P1)...must be either: • In the necessity of its own nature, or • In an external cause. - If the universe’s explanation is in an external cause, that cause itself cannot be contingent in the same way, or we simply push the question back. - Ultimately we must arrive at a being that exists by a necessity of its own nature: a necessarily existing, uncaused reality. (5) The only plausible candidate is something like a mind, a personal being. - Abstract objects, if they exist, are necessary and immaterial, but causally inert; they cannot bring a universe into existence. - A necessarily existing, immaterial, timeless, powerful cause capable of producing a contingent universe is best understood as a personal, rational agent. This is what classical theism means by “God”: a necessary, eternal, immaterial, personal Creator of all contingent reality.
(P4) The universe exists (and is not nothing). (1) The existence of the universe is a datum of experience. - We are directly aware of ourselves and the world around us. - Denying the universe’s existence is self-defeating; it uses the very existence of a thinker and thoughts to doubt that there is anything. (2) The question is not whether the universe exists, but why it exists. - The argument grants the obvious: the universe is real. - It asks a deeper, metaphysical question: what explains the existence of this contingent reality rather than nothing? Therefore, we have a contingent universe that clearly exists and calls for an explanation.
(C) Therefore, the best explanation for the existence of the contingent universe is a necessarily existing, eternal, immaterial, non-physical, extremely powerful, personal being...God.
Teleological
Cosmic Fine-Tuning
(P1) The fundamental constants and quantities of the universe are finely tuned for the existence of physical, interactive life. Fine-tuning describes the extreme sensitivity of life-permitting conditions to the numerical values of basic physical constants and initial conditions. (1) Fundamental constants and quantities. - Examples include: • The gravitational constant (G). • The cosmological constant (Λ) governing the expansion rate of the universe. • The ratio of the strengths of fundamental forces. • The distribution of mass and energy in the early universe. - These values are not determined by the known laws of nature; they are inputs to those laws. (2) Incredibly narrow life-permitting ranges. - If G differed by about 1 part in 10^60, no stars or planets could form; the universe would either disperse too rapidly or collapse into a single mass. - If Λ differed by about 1 part in 10^120, the universe would expand too quickly or too slowly for galaxies and chemistry to form. - If the initial distribution of mass–energy in the early universe were not even to about 1 part in 10^(10^123), the universe would be hostile to life of any kind. (3) These are razor-thin intervals in a vast space of possible values. - Imagine a dial for each parameter, divided into an enormous number of possible settings. - The life-permitting settings occupy an unimaginably tiny region compared to the total range of possibilities. - Shifting any of several constants or initial conditions by a “hair’s breadth” (in relative terms) leads to a life-prohibiting universe. (4) The fine-tuning is general and systematic. - It is not a single lucky coincidence; many independent constants and quantities must be simultaneously set within narrow life-permitting windows. - Physicists of diverse worldviews (theistic and non-theistic) acknowledge the reality and striking character of this fine-tuning. Therefore, our universe exhibits highly precise, multi-parameter fine-tuning for the possibility of physical, interactive life.
(P2) The fine-tuning of the universe is not plausibly due to physical necessity. (1) The laws of nature do not fix the relevant values. - Current fundamental theories treat constants (like G, Λ, particle masses, coupling constants) as free parameters. - The equations describe how things behave given certain values; they do not dictate that those values must be what they are. (2) Life-prohibiting universes appear completely possible physically and mathematically. - The same equations allow a vast range of values for these parameters; most such values yield universes without stable stars, chemistry, or complex structures. - Nothing in our best physics implies that only life-permitting universes are possible. (3) No independent argument shows that a life-permitting universe is necessary. - To claim “the universe had to be life-permitting” requires strong evidence that alternative values are impossible. - Instead, the scientific consensus is that different values are entirely compatible with the basic framework of our theories. (4) Appeals to an unknown future “theory of everything” are speculative. - It is conjectural to suppose that some future theory will uniquely fix all constants in a life-permitting way. - Even if such a theory existed, one could still ask: • Why that theory, with that structure and those constraints, rather than some other? • Why a theory that yields a life-permitting universe instead of countless life-prohibiting ones? Therefore, it is highly implausible that the fine-tuning of the universe is explained by physical necessity alone.
(P3) The fine-tuning of the universe is not plausibly due to chance, even given multiverse proposals. (1) The probabilities against fine-tuning by blind chance are astronomically small. - The life-permitting intervals for key constants and initial conditions are tiny compared to the range of possible values. - When many independent parameters must simultaneously fall into their narrow windows, the joint probability under “blind chance” becomes vanishingly small. (2) A single-universe chance hypothesis makes fine-tuning wildly surprising. - On a single-universe picture with no further structure, it is far more likely that the constants and initial conditions would fall into a life-prohibiting range. - The fact that we observe a richly life-permitting universe is thus highly unexpected under pure chance. (3) Multiverse proposals are highly speculative and face serious challenges. - There is currently no direct empirical evidence for a vast ensemble of other universes. - Most multiverse models rely on a “universe generator” with its own deep laws and conditions, which itself would appear to require fine-tuning. - Simply pushing fine-tuning back one level (to the generator or meta-laws) does not remove the need for explanation. (4) The “Boltzmann brain” problem undermines many multiverse accounts. - In a sufficiently large multiverse, small local fluctuations of order (e.g., a single self-aware “brain” surrounded by chaos) are vastly more probable than a whole, large, orderly, life-permitting universe like ours. - If our existence were a random sample from a multiverse, we should expect to find ourselves as isolated minimal observers in a small patch of order, not as embodied beings in a vast, stable, lawful cosmos with billions of other observers. (5) Chance plus selection effect (anthropic reasoning) is not enough. - The anthropic principle (“we can only observe a universe compatible with our existence”) is true but trivial if left by itself. - It tells us that observers will only find themselves in life-permitting universes; it does not explain why there is a finely tuned, life-permitting universe (or multiverse) at all, rather than only life-prohibiting reality. Therefore, whether in a single-universe or multiverse setting, blind chance does not provide a satisfying or plausible explanation of cosmic fine-tuning.
(P4) If a complex, highly improbable feature of the universe is not due to physical necessity or chance, then the best explanation is intelligent design. (1) Inference to the best explanation is a standard form of reasoning. - In science and everyday life, we often infer intelligent agency when we encounter: • High improbability under chance, • Combined with an independently recognizable pattern or function. - Examples: information in a message, complex machines, finely calibrated systems for specific goals. (2) Fine-tuning has the right structure for a design inference. - It is incredibly improbable on blind chance or unknown necessity. - It is precisely the sort of arrangement one would expect if a powerful, intelligent agent intended a universe capable of supporting life. (3) Design has strong explanatory power and scope. - A designing mind can directly choose and set the values of constants and initial conditions to achieve a life-permitting universe. - This single hypothesis accounts for a broad range of fine-tuning facts more naturally and simply than competing explanations. (4) A designing intelligence behind the universe must be transcendent. - The designer would have to stand beyond the physical universe (since the universe’s basic parameters themselves are what are being explained). - Thus the fine-tuning argument points to a powerful, intelligent, non-physical cause of the universe’s basic structure. Therefore, given the data of fine-tuning and the failure of necessity and chance, the best explanation is that the universe’s life-permitting structure is due to intelligent design.
(C) Therefore, the fine-tuning of the universe for life is best explained by a transcendent, intelligent Designer...an extremely powerful, non-physical mind, which is what classical theism calls God.
Applicability of Mathematics
(P1) If God does not exist, the applicability of mathematics to the physical world is just a happy coincidence. On naturalism, mathematical entities (numbers, sets, functions, equations) are non-physical and causally inert. They cannot cause anything in the physical world. So if there is no divine mind ordering reality, the fact that the physical universe behaves in precise accordance with abstract mathematics is, at best, an unexplained coincidence.
(P2) The applicability of mathematics to the physical world is not just a happy coincidence. Mathematics does not merely organize data after the fact; it successfully predicts new phenomena (e.g., planets, radio waves, the Higgs boson) using highly abstract structures (imaginary numbers, higher-dimensional spaces, etc.). As Eugene Wigner put it, the “unreasonable effectiveness of mathematics” is so striking that he called it a “miracle which we neither understand nor deserve.”
(C1) Therefore, God exists.
Moral & Rational
The Moral Argument
(P1) If God does not exist, then objective moral values and duties do not exist. (1) “Objective” moral values and duties. - A moral value is objective if it is true or false independently of what any individual or culture thinks. - A duty is objective if we are really obligated to do (or not do) something, whether we feel like it or not. - Example: “Torturing children for fun is wrong” is taken to be objectively wrong for everyone, everywhere, whether or not anyone believes it. (2) Without God, there is no adequate foundation for objective moral values. - On atheism, reality at bottom is just matter, energy, and blind physical processes. - There is no personal, moral standard “above” human beings; there is only: • What helps survival or reproduction, • What individuals or societies happen to approve or disapprove of. - In such a world, judgments like “kindness is good” or “racism is evil” cannot be grounded in anything beyond human opinion or feeling. (3) Without God, there is no adequate foundation for objective moral duties. - Duties are owed to persons; moral obligations are like commands or requirements placed on us. - If there is no divine Lawgiver, then: • Who or what imposes moral obligations on us? • Why are we really bound to act in one way rather than another? - On a naturalistic view where humans are highly evolved animals, our behaviors are more like instinctive patterns, not morally required or forbidden actions. (4) A God-centered account offers a natural foundation. - God’s unchanging, perfectly good nature provides an objective standard of moral value. - God’s commands, flowing from His nature (e.g., “love your neighbor as yourself”), ground moral duties: what we truly ought to do. Therefore, if there is no God...no transcendent, perfectly good personal Lawgiver...then there is no solid basis for objective moral values or duties; morality collapses into subjectivity or convention.
(P2) Objective moral values and duties do exist; some things are really good or evil, right or wrong, independent of human opinion. (1) Our moral experience presents moral facts as objective. - We experience certain actions (e.g., child abuse, genocide, racism, terrorism) as truly wrong, not merely “unpopular” or “personally distasteful.” - Likewise, we recognize virtues like generosity, self-sacrifice, and fairness as truly good, not just personally or culturally preferred. (2) To deny objective morality is extremely counterintuitive. - Saying “there is nothing really wrong with torturing infants for fun” or “rape and racial genocide are not objectively evil” conflicts with our deepest moral intuitions. - The person who claims “morality is just preference” still protests, “That’s not fair! That’s unjust!”...implicitly affirming objective moral standards. (3) Moral realism is analogous to realism about the external world. - Just as our sense experience gives us strong prima facie grounds to believe in a physical world, our moral experience gives us strong grounds to believe in objective moral norms. - To treat all moral experience as completely illusory requires powerful defeaters, which are lacking. (4) Widespread moral disagreement does not overturn objectivity. - People disagree about many things (science, history, politics), but we do not infer that there is no objective truth in those domains. - Disagreement often concerns facts, application, or background beliefs, not whether there is any objective right answer at all. Therefore, it is far more reasonable to affirm than to deny that some moral values and duties are objectively real and binding.
(C) Therefore, God exists: the reality of objective moral values and duties points to a transcendent, perfectly good Lawgiver and moral standard.
Free-Thinking Argument
(P1) If robust naturalism is true, then God or things like God do not exist. Robust naturalism is the view that only physical things exist...no God, no immaterial souls, no abstract minds. Reality is exhausted by space-time, matter/energy, and the laws of nature.
(P2) If God or things like God do not exist, then humanity does not freely think in the libertarian sense. On a purely naturalistic picture, all human thoughts are the result of prior physical causes (e.g., brain chemistry, genetics, environment). This yields at best determinism (or indeterministic randomness), not genuine libertarian freedom to choose between alternatives in our thinking.
(P3) If humanity does not freely think in the libertarian sense, then humanity is never epistemically responsible. To be epistemically responsible...to be genuinely praiseworthy or blameworthy for what we believe...we must have some control over our thinking: we must be able to assess reasons, weigh evidence, and choose between competing beliefs. If our beliefs are entirely fixed by non-rational, prior physical causes, we are not truly responsible for holding them.
(P4) Humanity is occasionally epistemically responsible. In ordinary life we routinely treat people (including ourselves) as genuinely responsible for at least some of their beliefs...e.g., for ignoring evidence, being intellectually dishonest, or carefully weighing arguments. Our practices of rational praise and blame presuppose that people sometimes can freely choose how to respond to reasons.
(C1) Therefore, humanity freely thinks in the libertarian sense. (from P3 and P4, modus tollens)
(C2) Therefore, God or things like God exist. (from P1 and P2 and C1)
(C3) Therefore, robust naturalism is false. (from P1 and C2, modus tollens)
(P5) The biblical account of reality is one possible explanation for the existence of God, things like God, and the libertarian freedom of humanity.
(P6) If the biblical account provides a better explanation of these facts than alternative accounts, then it is reasonable to accept it as the best explanation.
(C4) Therefore, if the biblical account provides the best explanation, it is reasonable to accept it. (from P5 and P6, abduction to the best explanation)
Evolutionary Argument Against Naturalism (EAAN)
(P1) If naturalism and unguided evolution are both true, then the probability that our cognitive faculties are reliable is low or inscrutable. On naturalism, humans are the result of unguided evolutionary processes aimed at survival and reproduction, not at producing true beliefs as such. Evolution selects for behavior that enhances fitness, whether or not the underlying beliefs are true.
(P2) If the probability that our cognitive faculties are reliable is low or inscrutable, then we have a defeater for trusting the deliverances of those faculties. If you have good reason to doubt that your thinking is generally truth-tracking, then you also have good reason to doubt the beliefs produced by that thinking...including your belief in naturalism and evolution themselves.
(P3) If we have a defeater for trusting our cognitive faculties, then we have a defeater for any belief produced by those faculties, including belief in naturalism and unguided evolution. Belief in naturalism and in the truth of evolutionary theory is itself formed by our cognitive faculties. So if those faculties are undercut, these beliefs are undercut as well.
(P4) Therefore, if naturalism and unguided evolution are both true, we have a defeater for believing that naturalism and unguided evolution are true. (from P1–P3)
(C1) Therefore, naturalism is self-defeating and cannot be rationally affirmed together with unguided evolution.
(P5) Theism offers a better explanation of the reliability of our cognitive faculties than naturalism with unguided evolution. On theism, a rational God creates humans in His image with cognitive faculties designed for truth, not merely for survival. This gives us a positive reason to trust our minds as generally reliable.
(C2) Therefore, the reliability of our cognitive faculties provides evidence in favor of theism over naturalism.
Modal Ontological (Maximal Greatness)
(P1) It is possible that a maximally great being exists. A "maximally great being" is one that has maximal excellence (omnipotence, omniscience, moral perfection, etc.) in every possible world. In other words, if such a being exists, it exists necessarily and cannot fail to exist.
(P2) If it is possible that a maximally great being exists, then a maximally great being exists in some possible world. In modal logic, "possibly exists" means "exists in at least one possible world" (a complete way reality could have been).
(P3) If a maximally great being exists in some possible world, then it exists in every possible world. By definition, a maximally great being has necessary existence. If such a being exists in any possible world, it must exist in all possible worlds (it cannot be "contingent").
(P4) If a maximally great being exists in every possible world, then it exists in the actual world. The actual world is one of the possible worlds. If a being exists in every possible world, it exists in this one too.
(P5) If a maximally great being exists in the actual world, then a maximally great being exists. If such a being exists in our world, then it simply exists...God is real.
(C1) Therefore, a maximally great being exists.
Five Ways
First Way – From Motion/Change
(P1) Things in the world are in motion (undergoing change). By “motion,” Aquinas means change in a broad sense (e.g., from potential to actual): local motion, growth, decay, heating, cooling, etc. Our everyday experience and all of natural science presuppose that real change occurs.
(P2) Whatever is moved (changed) is moved by another. A thing cannot be actually changing in respect of some feature while remaining purely potential in that same respect, all by itself. For example, a piece of wood does not go from cold to hot by itself; it is heated by something already hot. Change from potentiality to actuality requires something already actual as its cause.
(P3) There cannot be an infinite regress of essentially ordered movers (causes of motion). In a here-and-now (essential) causal series...like a hand moving a stick moving a stone...the intermediate movers have causal power only by being moved/actualized by something prior in the series. If there were no first actualizer in such a series, there would be no motion at all, just as a train of cars cannot move without some engine.
(C1) Therefore, there exists a first unmoved mover: something that causes motion (change) in others without itself being moved (changed) by another in the same way.
(C2) This first unmoved mover is what we call God.
Second Way – From Efficient Cause
(P1) In the world of sense, we find an order of efficient causes. By an “efficient cause,” Aquinas means that which brings something into being or sustains it (e.g., a builder causing a house, fire causing heat, parents causing a child). Our experience and all of science presuppose that things have causes.
(P2) Nothing can be the efficient cause of itself. If something caused itself to exist, it would have to exist before it existed, which is impossible. A cause must be distinct from its effect at least in the order of explanation: the effect depends on the cause, not vice versa.
(P3) There cannot be an infinite regress of essentially ordered efficient causes. In an essentially ordered series of causes (here-and-now dependence), intermediate causes have causal power only because they receive it from prior causes. If there were no first cause in such a series, there would be no causal activity at all, like a series of gears with no primary driving gear.
(C1) Therefore, there must be a first efficient cause that is not itself caused by anything else.
(C2) This first uncaused cause is what we call God.
Third Way – From Contingency
(P1) There are contingent beings in the world...things that can exist and can fail to exist. A contingent being is one that does not have to exist; it begins to exist and can cease to exist (e.g., people, animals, stars, planets). We observe that such things come into being and pass away, and so their existence is not necessary.
(P2) If everything were contingent, then at some time nothing would have existed. If every being could fail to exist, then there is no guarantee that something or other would always exist. Given enough “time” or possibilities, there would be a state of affairs in which nothing at all existed.
(P3) If at some time nothing existed, then nothing would exist now. From absolute nothingness, nothing comes. If there were ever a total absence of being, nothing could begin to exist, because there would be nothing with the power to bring anything into existence.
(P4) But something does exist now (including ourselves and the world around us). Our present existence is undeniable. It follows that it cannot be the case that only contingent beings have ever existed.
(C1) Therefore, not all beings are contingent; there must exist at least one necessary being that cannot fail to exist.
(P5) A necessary being either has the cause of its necessity in itself or from another. Either the necessary being’s existence is explained by its own nature (it exists “of itself”), or it is necessary because something else makes it so.
(P6) There cannot be an infinite regress of necessary beings whose necessity is caused by another. An endless chain of beings whose necessary existence is borrowed from earlier beings would never explain why there is any necessary existence at all. There must be a necessary being that has the cause of its necessity in itself and does not derive it from another.
(C2) Therefore, there exists a necessary being that has its necessity in itself and is the cause of the existence of all contingent beings.
(C3) This necessary being is what we call God.
Fourth Way – From Degrees of Perfection
(P1) Among things, we find degrees of perfection (more or less good, true, noble, etc.). We naturally compare things in terms of value and excellence: some actions are better than others; some people are wiser, more just, or more loving than others; some beings have fuller reality or goodness than others (e.g., a rational person vs. a rock).
(P2) Degrees of a quality (like goodness or truth) are understood by comparison to a maximum or standard of that quality. When we say one thing is “hotter” or “colder,” “truer” or “better,” we implicitly measure it against some maximum or fullest instance. Aquinas (drawing on Aristotle) holds that gradations in a transcendental property (goodness, truth, nobility) imply a reference to something that possesses that property fully or maximally.
(P3) Therefore, if there are degrees of goodness, truth, and nobility in things, there must be something that is maximally good, maximally true, and maximally noble. This “maximum” is not just a useful fiction or idealization, but a real standard in terms of which all lesser participations in goodness and truth are measured and made intelligible.
(P4) What is maximally true and good is the cause of all that is true and good in other things. Aquinas argues that in any genus, the maximum is the cause of the others in that genus (e.g., the hottest thing is the cause of heat in other things). By analogy, the supreme source of goodness and truth causes and sustains all finite instances of goodness and truth.
(C1) Therefore, there exists something that is the maximum and source of all perfections such as goodness, truth, and nobility in things.
(C2) This maximally perfect being is what we call God.
Fifth Way – From Finality / Teleology
(P1) Non-rational things in nature regularly act for an end (toward goals or purposes). Aquinas notes that natural objects and processes...like acorns becoming oak trees, hearts pumping blood, planets following stable paths, and physical laws yielding orderly outcomes...consistently behave in ways that tend toward certain effects rather than others. They exhibit regular, goal-directed behavior.
(P2) Whatever lacks knowledge cannot direct itself to an end unless it is directed by something with knowledge and intelligence. An arrow does not fly toward a target by itself; it is aimed by an archer. Likewise, entities that have no awareness or understanding (e.g., physical particles, plants, organs) cannot by themselves “aim” at ends. Their consistent tendency toward certain outcomes calls for explanation in terms of an ordering intelligence.
(C1) Therefore, natural things that lack knowledge and yet act for an end must be directed by some being endowed with knowledge and intelligence.
(C2) This intelligent director of nature is what we call God.