The concept of determinism conveys the idea that everything that happens could not have happened in a different way than it actually did. Or alternatively, everything that happens, happens by necessity. However, as simple as this may sound, the concept of determinism is one of the most difficult and controversial concepts in Western philosophy. Philosophers often distinguish different kinds of determinism. First, there is scientific determinism, which was inspired by classical physics. One interpretation entails that everything in the universe is governed by universal laws. Universalin this context means that the laws are the same everywhere in the universe and at all times, and that they apply to all events and objects.
A second interpretation of scientific determinism holds that every event has a sufficient cause. These two interpretations of scientific determinism combined can yield an argument for Laplacian determinism: If every event has a sufficient cause, and if every event is governed by universal laws, then one could in principle predict exactly the subsequent evolution of the universe if one had knowledge of all the initial conditions of all objects in the universe combined with knowledge of all the laws of nature.
Since the second half of the twentieth century, however, more and more scientists argue that not all natural laws are deterministic, but that some of these laws may be inherently statistical in nature. This line of argument could constitute an argument for indeterminism, and is explored further by Karl Popper (1902–1994). Furthermore that, though Laplacian determinism is an ontological view, it is mostly formulated in epistemic terms, relating to knowledge and predictive capabilities. One must keep in mind that scientific determinism is first of all a claim about how the world is constituted. As such one must distinguish this ontological claim from the epistemological claim to predictability, even though both often go together. That determinism does not always entail predictability is testified by chaotic systems, which display deterministic though unpredictable behavior.
If scientific determinism is taken seriously, it can result in a worldview that affirms the concept of metaphysical determinism. Metaphysical determinism conveys the idea that if everything in the universe is governed by universal laws, and if every event has a sufficient cause, then there is only one history possible. One can clarify this idea by using possible-world semantics. If a possible world starts off with exactly the same initial conditions as the actual world and with exactly the same universal laws, its evolution would look the same in every detail. As such, metaphysical determinism entails scientific determinism, but not necessarily vice versa, even though scientific determinism could be used to defend metaphysical determinism.
Both metaphysical and scientific determinism are threatened by the indeterminism of quantum mechanics, when interpreted as an ontological feature of the world. If at the quantum level there is genuine indeterminism, then, it might be argued, not everything has a sufficient cause, so that the histories of two possible worlds with exactly the same initial conditions, but with quantum indeterminism, might develop in completely different ways. However, scientists like David Bohm (1917–1992) have tried to restore determinism at the quantum level by invoking hidden variables, though this proposal is not uncontroversial. Furthermore, it must be kept in mind that quantum theory might not be the final theory, but might in the future be replaced by an alternative theory that forces its philosophical interpretation to affirm either determinism or indeterminism.
A third kind of determinism, closely related to scientific determinism, is mathematical determinism. Mathematical determinism is the “logical” complement of scientific determinism, and has become increasingly important in chaos theory. In mathematical determinism the initial conditions are numerical inputs, and a mathematical function takes the place of the universal law. Mathematical determinism now entails that, given an arbitrary value of the initial conditions, calculating the mathematical function will yield one and only one outcome.
In other words, given an arbitrary value of the initial conditions and a mathematical function, there is only one outcome possible. In the case of mathematical chaotic systems, problems arise with specifying the initial value. Because knowledge of the initial conditions is limited, the outcome of a chaotic evolution cannot be predicted, yet as a mathematical system it is deterministic, which means that the outcome of the calculation, given the initial conditions, could not be other than it actually is.
A fourth kind of determinism is logical determinism. Logical determinism is about propositions, and entails that any proposition about the past, present, or future of the world is either true or false. As such, logical determinism is grounded in Aristotle’s law of the excluded middle, which holds that a proposition cannot be both true and false at the same time. Developments in so-called “fuzzy logic” have challenged this kind of determinism. Theological determinism constitutes a fifth kind of determinism. There are two types of theological determinism, both compatible with scientific and metaphysical determinism. In the first, God determines everything that happens, either in one all-determining single act at the initial creation of the universe or through continuous divine interactions with the world.
Either way, the consequence is that everything that happens becomes God’s action, and determinism is closely linked to divine action and God’s omnipotence. According to the second type of theological determinism, God has perfect knowledge of everything in the universe because God is omniscient. And, as some say, because God is outside of time, God has the capacity of knowing past, present, and future in one instance. This means that God knows what will happen in the future. And because God’s omniscience is perfect, what God knows about the future will inevitably happen, which means, consequently, that the future is already fixed.
All forms of determinism (except perhaps mathematical determinism) challenge the idea of free will. Or rather, they render the experience of free will an illusion. Theological determinism moreover raises big problems for the idea that God is perfectly good. For, if everything is God’s action, the evil and suffering that happens is also due to God’s actions. Or, alternatively, if God already knows what evil will happen, why does God not prevent it from happening? Some theologians have argued for divine self-limitation (kenosis) of God’s omniscience and omnipotence to warrant human freedom.
(Author is a Research Scholar in Sociology and can be reached at firstname.lastname@example.org)