How did Kant argue that lying treats people as means rather than ends?

Immanuel Kant argued that morality is rooted in our capacity for free, rational choice, and he maintained that we have a moral duty to treat all rational beings as ends in themselves—meaning they possess intrinsic value—rather than merely as means to an end.12

When a person lies, they attempt to manipulate the listener by inducing a false belief, which undermines the listener's capacity to make their own free, rational decisions based on the truth. By deceiving someone, the liar treats that person as an instrument to achieve a personal goal rather than as a rational agent with their own intrinsic worth. Consequently, Kant viewed lying as an assault on morality itself, as it violates the requirement to respect the autonomy and rational agency of others.12