Coercion (co-er-shion) is the practice of compelling a person or manipulating them to behave in an involuntary way (whether through action or inaction) by use of threats, intimidation or some other form of pressure or force. These are used as leverage, to force the victim to act in the desired way. Coercion may involve the actual infliction of physical pain/injury or psychological harm in order to enhance the credibility of a threat. The threat of further harm may then lead to the cooperation or obedience of the person being coerced. Torture is one of the most extreme examples of coercion i.e. severe pain is inflicted on victims until they give interrogators the desired information.

The term is often associated with circumstances which involve the unethical use of threats or harm to achieve some objective. Coercion may also serve as a form of justification for a conclusion in a logical fallacy or non-logical argument.

Coercion may also refer to more subtle means of influence such as sweet talking, begging, charming, and seduction.

Overview

Any person's set of feasible choices is obtained from the combination of two elements: the initial endowment (the perceived initial state of the world, which the chosen actions are going to affect) and the transformation rules (which state how any chosen action will change the initial endowment, according to the person's perception).

It follows that coercion could in principle take place by purposely manipulating either the transformation rules or the initial endowment (or both). In practice, however, the detailed choice reaction of a victim to a change in initial endowment is generally unpredictable. Hence effective coercion can only be carried out through manipulation of the transformation rules. This is done by the credible threat of some injury, conditional on the victim's choice. Often, it involves the actual inflicting of injury in order to make the threat credible, but it is the threat of (further) injury which brings about the change in transformation rules.

Coercion does not remove entirely the victim's ability to choose, nor does it necessarily affect his or her ranking of potential alternatives. As Roman jurists used to say, coactus volui, tamen volui (I willed under coercion, but still I willed). In the terminology of rational choice theory, coercion does not remove a person's objective function, but only affects the constraints under which such function is maximised. Yet, the purpose of coercion is to substitute one's aims to those of the victim. For this reason, many social philosophers have considered coercion as the polar opposite to freedom.

Various forms of coercion are distinguished: first on the basis of the kind of injury threatened, second according to its aims and scope, and finally according to its effects, from which its legal, social, and ethical implications mostly depend.