In everyday life the word identity is rarely used — although in many states one is expected to carry an identity card that designates one as the citizen of a specific country. It confirms one's status as a subject under the law of this state, with rights and obligations. The specific link with this state founds the person's rights in foreign countries in contexts determined by contracts between different states. With the identity card or the passport, the state assures that it really is this specific person, who is accepted as citizen and not another one who is not entitled to claim, for example, social rights. We touch here on the problems of (illegal) immigration and international crime with forged papers. To assure that it actually is this person who has the attributed status, and not some impostor, the state relies on certain criteria such as height, the colour of skin, hair and eyes, the date and place of birth. These criteria are not always sufficient to determine the identity of a person. The police also use finger prints and more recently, numerical checks of the iris. The question that arises here is, what concept of identity is at work in these practices?