Final answer:
d'Holbach's "thirsty man" example illustrates his argument that human actions are determined by biological needs, challenging the concept of free will.
Step-by-step explanation:
The purpose of d'Holbach's "thirsty man" example was to demonstrate that human actions, such as the act of drinking water when thirsty, are determined by the needs and constraints of the human body, rather than by free will. d'Holbach argues that, just as a thirsty man is compelled by his body's demands to seek water, all human actions are influenced by various determinants, either internal or external. This notion supports d'Holbach's deterministic view that free will is an illusion, and that all events, including human actions, are the inevitable result of preceding causes.