In both science and religion there is a lively debate about the role of chance in the universe. In science, this debate usual takes the form of a discussion deciding between determinism (all events follow of necessity from prior initial conditions) and physical indeterminism (some events, at least, are not so determined). In religion, the dispute is between those who accept total predestination (the view that God unilaterally ordains everything that happens) and theological indeterminism (God leaves some things to chance or to determination by finite agents). Most religious views deny any role for pure chance, but many allow some role for chance even in a providentially-governed universe. Debate is often clouded by a failure to define what "chance" is.

Different senses of chance

In its most radical sense, chance is the occurrence of an event without any cause or reason. Thus the universe may be said to come into existence for no reason and without any antecedent cause—by chance. In this sense, absolutely anything might happen at any time, and there is no point in seeking reasons for what happens. If everything happened by chance, in this sense, science would be impossible.

Another, more common, sense of chance is involved in gambling or lotteries. When a gambler throws a die, the side that lands uppermost is a matter of chance. It is not that there are no causes for the position of the die, but that the causes are far too difficult, complex, or tedious to be detected. The roll of the die could be determined in every particular by applying the laws of mechanics, but it would still be considered a matter of chance because the system is set up so that no human can predict the outcome. In this case, chance primarily refers to unpredictability; whether something is chance or not depends on the knowledge available to the observer.

Another sense is that in which something happens "by chance" because it is not intended by any agent. A person may meet a long-lost friend by chance if neither the person nor the friend nor God had intended the meeting to happen, or tried to bring it about. Genetic mutations are said to be random, to occur by chance, in this sense. They have causes, but they are not intended to happen as they do.

This sense can be extended to events that are not parts of any directional process or propensity. Thus, many geneticists would say that genetic mutations do not tend in any particular direction (they do not, for example, always occur so as to maximize the chances of survival for some organism). This view is contentious, for some argue that there are propensities in organic mutation; the process does tend to realize consciousness eventually, and this tendency is inbuilt in the system from the beginning. If this were true, particular mutations could happen by chance (they would not each be determined to increase the chances of consciousness coming into being), but the process as a whole (the whole set of mutations in their environmental context) might have a propensity to terminate in consciousness.

This introduces yet another sense of chance, for which particular events have a specific probability of occurring, but are not sufficiently determined. An event is sufficiently determined when, given its initial conditions and the laws of nature, it could not happen in any other way. An event is not sufficiently determined when, from the very same initial conditions and laws, there are a number of possible effects that could result. In other words, the same cause in the same situation can have different effects. Some physicists have denied this possibility, but the Copenhagen Interpretation of quantum mechanics asserts precisely that particular subatomic events have a highly specific probability of occurring in a specific way, but they may not do so. When large numbers of quantum events occur, however, this probability will turn into a predictable certainty—thus the equations of quantum mechanics are deterministic, though they refer to events that are to some extent indeterminate. Such processes are called "stochastic"; there is a high probability that specific types of events will occur, but particular events may be unpredictable and not sufficiently determined.

Implications for freedom

There are thus two main components of the idea of chance—lack of predictability and lack of sufficient causality. For some philosophers, human freedom requires chance, since humans could not be held responsible for their actions if they were sufficiently caused (if they were determined by some cause, whether natural or divine) to act as they do. According to this view, chance is a necessary condition of responsible freedom. A free act is distinguished from a purely arbitrary (non-caused) act by being intentional, initiated for a purpose.

A believer in God may say that the creation of the universe is the primary instance of a free act. Creation is not caused by any prior initial state or by some general laws, but it is brought about for a reason. God has some value or values in mind, and realizes them by creating the universe. A free act is thus a form of causality for the sake of realizing some envisaged value. This causality distinguishes such an act sharply from pure chance, even though the act may appear unpredictable and undetermined from the point of view of physical laws and prior physical or mental states.

Some theologians have proposed that quantum mechanics shows the fundamental laws of the universe to be stochastic, or statistical, rather than deterministic. This, they claim, would permit both human free acts to occur, and would also allow God to act freely within the statistical probabilities of the physical system without "breaking" any laws of nature. For others, it is much too restrictive to confine God's free actions to scrabbling around in the sub-atomic basement. In any case, quantum indeterminacies cancel out because of the large numbers of probabilistic events involved in supra-atomic events, which means that the overall statistical distribution is virtually uncertain.

The existence of dynamic systems far from equilibrium allows quantum fluctuations to be amplified to produce macrocosmic effects. Thus in the right circumstances (in the brain, for example) quantum indeterminacies could produce huge observable indeterminacies in nature. Or it could be held that, quantum considerations apart, laws of nature are in themselves probabilistic, operating on an "other things being equal" basis, and they do not exclude free, or teleological causality, at all.

Religious views cannot easily live with any supposition of pure chance, in the radical sense. Most classical theistic views are deterministic (all is determined by God), seeing freedom as compatible with determinism. But in the twentieth century there has been an increase in the number of people holding nondeterministic views, for which chance (as probabilistic indeterminism) allows free creative activity both of creatures and of God, and a mutual responsiveness of creaturely and divine acts that may be held to be close to a biblical perspective.

See also COMPLEXITY; CONTINGENCY; CONVERGENCE

KEITH WARD