then there is an infinitely long chain of causes of change. But, it is alleged, there cannot be a causal chain of infinite length. Therefore there is something that causes change, but is not caused to change by anything else, i.e., a first cause. Many critics of this form of the argument deny its assumption that there cannot be an infinite causal regress or chain of causes. This argument also fails to show that there is only one first cause and does not prove that a first cause must have such divine attributes as omniscience, omnipotence, and perfect goodness.
A version of the cosmological argument that has attracted more attention from contemporary philosophers is the argument from contingency to necessity. It starts with the observation that there are contingent beings – beings that could have failed to exist. Since contingent beings do not exist of logical necessity, a contingent being must be caused to exist by some other being, for otherwise there would be no explanation of why it exists rather than not doing so. Either the causal chain of contingent beings has a first member, a contingent being not caused by another contingent being, or it is infinitely long. If, on the one hand, the chain has a first member, then a necessary being exists and causes it. After all, being contingent, the first member must have a cause, but its cause cannot be another contingent being. Hence its cause has to be non-contingent, i.e., a being that could not fail to exist and so is necessary. If, on the other hand, the chain is infinitely long, then a necessary being exists and causes the chain as a whole. This is because the chain as a whole, being itself contingent, requires a cause that must be noncontingent since it is not part of the chain. In either case, if there are contingent beings, a necessary being exists. So, since contingent beings do exist, there is a necessary being that causes their existence. Critics of this argument attack its assumption that there must be an explanation for the existence of every contingent being. Rejecting the principle that there is a sufficient reason for the existence of each contingent thing, they argue that the existence of at least some contingent beings is an inexplicable brute fact. And even if the principle of sufficient reason is true, its truth is not obvious and so it would not be irrational to deny it. Accordingly, William Rowe (b.1931) concludes that this version of the cosmological argument does not prove the existence of God, but he leaves open the question of whether it shows that theistic belief is reasonable.
The starting point of teleological arguments is the phenomenon of goal-directedness in nature. Aquinas, e.g., begins with the claim that we see that things which lack intelligence act for an end so as to achieve the best result. Modern science has discredited this universal metaphysical teleology, but many biological systems do seem to display remarkable adaptations of means to ends. Thus, as William Paley (1743–1805) insisted, the eye is adapted to seeing and its parts cooperate in complex ways to produce sight. This suggests an analogy between such biological systems and human artifacts, which are known to be products of intelligent design. Spelled out in mechanical terms, the analogy grounds the claim that the world as a whole is like a vast machine composed of many smaller machines. Machines are contrived by intelligent human designers. Since like effects have like causes, the world as a whole and many of its parts are therefore probably products of design by an intelligence resembling the human but greater in proportion to the magnitude of its effects. Because this form of the argument rests on an analogy, it is known as the analogical argument for the existence of God; it is also known as the design argument since it concludes the existence of an intelligent designer of the world. Hume subjected the design argument to sustained criticism in his Dialogues Concerning Natural Religion. If, as most scholars suppose, the character Philo speaks for Hume, Hume does not actually reject the argument. He does, however, think that it warrants only the very weak conclusion that the cause or causes of order in the universe probably bear some remote analogy to human intelligence. As this way of putting it indicates, the argument does not rule out polytheism; perhaps different minor deities designed lions and tigers. Moreover, the analogy with human artificers suggests that the designer or designers of the universe did not create it from nothing but merely imposed order on already existing matter. And on account of the mixture of good and evil in the universe, the argument does not show that the designer or designers are morally admirable enough to deserve obedience or worship. Since the time of Hume, the design argument has been further undermined by the emergence of Darwinian explanations of biological adaptations in terms of natural selection that give explanations of such adaptations in terms of intelligent design stiff competition. Some moral arguments for the existence of God conform to the pattern of inference to the best explanation. It has been argued that the hypothesis that morality depends upon the will of God provides the best explanation of the objectivity of moral obligations. Kant’s moral argument, which is probably the best-known specimen of this type, takes a different tack. According to Kant, the complete good consists of perfect virtue rewarded with perfect happiness, and virtue deserves to be rewarded with proportional happiness because it makes one worthy to be happy. If morality is to command the allegiance of reason, the complete good must be a real possibility, and so practical reason is entitled to postulate that the conditions necessary to guarantee its possibility obtain. As far as anyone can tell, nature and its laws do not furnish such a guarantee; in this world, apparently, the virtuous often suffer while the vicious flourish. And even if the operation of natural laws were to produce happiness in proportion to virtue, this would be merely coincidental, and hence finite moral agents would not have been made happy just because they had by their virtue made themselves worthy of happiness. So practical reason is justified in postulating a supernatural agent with sufficient goodness, knowledge, and power to ensure that finite agents receive the happiness they deserve as a reward for their virtue, though theoretical reason can know nothing of such a being. Critics of this argument have denied that we must postulate a systematic connection between virtue and happiness in order to have good reasons to be moral. Indeed, making such an assumption might actually tempt one to cultivate virtue for the sake of securing happiness rather than for its own sake.
It seems therefore that none of these arguments by itself conclusively proves the existence of God. However, some of them might contribute to a cumulative case for the existence of God. According to Richard Swinburne, cosmological, teleological, and moral arguments individually increase the probability of God’s existence even though none of them makes it more probable than not. But when other evidence such as that deriving from providential occurrences and religious experiences is added to the balance, Swinburne concludes that theism becomes more probable than its negation. Whether or not he is right, it does appear to be entirely correct to judge the rationality of theistic belief in the light of our total evidence.
But there is a case to be made against theism too. Philosophers of religion are interested in arguments against the existence of God, and fairness does seem to require admitting that our total evidence contains much that bears negatively on the rationality of belief in God. The problem of evil is generally regarded as the strongest objection to theism. Two kinds of evil can be distinguished. Moral evil inheres in the wicked actions of moral agents and the bad consequences they produce. An example is torturing the innocent. When evil actions are considered theologically as offenses against God, they are regarded as sins. Natural evils are bad consequences that apparently derive entirely from the operations of impersonal natural forces, e.g. the human and animal suffering produced by natural catastrophes such as earthquakes and epidemics. Both kinds of evil raise the question of what reasons an omniscient, omnipotent, and perfectly good being could have for permitting or allowing their existence. Theodicy is the enterprise of trying to answer this question and thereby to justify the ways of God to humans. It is, of course, possible to deny the presuppositions of the question. Some thinkers have held that evil is unreal; others have maintained that the deity is limited and so lacks the power or knowledge to prevent the evils that occur. If one accepts the presuppositions of the question, the most promising strategy for theodicy seems to be to claim that each evil God permits is necessary for some greater good or to avoid some alternative to it that is at least as bad if not worse. The strongest form of this doctrine is the claim made by Leibniz that this is the best of all possible worlds. It is unlikely that humans, with their cognitive limitations, could ever understand all the details of the greater goods for which evils are necessary, assuming that such goods exist; however, we can understand how some evils contribute to achieving goods. According to the soul-making theodicy of John Hick (b.1922), which is rooted in a tradition going back to Irenaeus, admirable human qualities such as compassion could not exist