Part of James Rachels's case for determinism involves the mention of twin studies that demonstrate cases of twins acting similarly.
Yes, James Rachels does discuss twin studies as part of his argument for determinism. He uses these studies to show that genetic factors, which are believed to largely determine our behavior and characteristics, contribute significantly to our actions. Twin studies involve comparing the behaviors and traits of identical twins (who share 100% of their genes) and fraternal twins (who share only about 50% of their genes). Rachels points out that if identical twins tend to exhibit greater similarity in their behavior compared to fraternal twins, it suggests that genetic factors play a significant role in shaping behavior.
By referencing these studies, Rachels aims to support the idea that our actions and choices are heavily influenced by factors beyond our control, such as our genetic makeup and biological predispositions. This aligns with the determinist perspective, which argues that all events and actions in the universe, including human behavior, are determined by causes that precede them.