In a broad sense, determinism is a theory or doctrine that suggests that occurrences of natural, social, or psychological phenomena and acts of the will are causally determined by preceding events or natural laws. In other words, determinism posits that all events, whether involving inanimate matter or conscious beings like humans, are influenced by previous events. It could be argued that if one were to have a complete understanding of the physical state of the universe at any given moment and all physical laws, one could, in principle, predict the future perfectly, including the so-called free actions of human beings.
In psychology, in particular, determinism holds that all human behaviours flow from genetic or environmental factors that, once they have occurred, are very difficult or impossible to change. For example, a determinist might argue that a person’s genes make them anxious. An extreme determinist might suggest that anxiety’s genetic basis makes it more challenging to alter, while a moderate determinist might argue that anxiety cannot be altered.
In the natural sciences, particularly in physics, determinism asserts that the laws of nature, such as Isaac Newton‘s laws of motion, are causal laws. As is well known, Newton’s laws are mathematical equations that function over time. It could be said that once the positions and velocities of all the particles in the universe are known, it is possible to input any time in the past or future, and these differential equations will tell us everything that has happened and ever can happen. In this idea of classical mechanics, it could be argued that the universe has but one past, the actual past, and it also has only one future, the only possible future, completely determined by those mathematical equations.
In philosophical terms, determinism is the belief that all events, including moral choices, are completely determined by previously existing causes. This understanding of determinism often leads to the conclusion that it precludes free will because it implies that humans cannot act otherwise than they do. The theory holds that the universe is utterly rational because complete knowledge of any given situation assures that knowing its future is also possible. For him, the present state of the universe is the effect of its previous state and the cause of the state that follows it. For Marquis de La Place, if a mind at any given moment could know all of the forces operating in nature and the respective positions of all its components, it would thereby have a better understanding of the future and the past of every entity, large or small. The Persian poet Omar Khayyám expressed a similar deterministic view of the world in the concluding half of one of his quatrains: “And the first morning of creation wrote what the last dawn of reckoning shall read.