The Social Security number (SSN) is thought of as such an identifier.
Technically it is not because people may have more than one number or more than one person may have the same number.
Thus, an internal, implanted microchip for identification of humans is already a reality.
Among the problematic issues in the introduction and regulation of a national identification card in Australia were: inaccurate, incomplete, irrelevant or misleading data and unauthorized disclosure of personal data.
The most serious overtone, however, was that "requiring each citizen to carry a government number is another step along the path of treating people as a 'national resource', which means government property, whereas the liberal democratic view has always been that the government is the people's 'property'."in response to pressures from Congressional representatives for action.
By contrast, a biometric identifier representing a particular human characteristic may be clearly matched to an individual.
Aside from the difficulties involved with the assignment of a reference number for each individual, other concerns came to light when a system for country-wide identification purposes was proposed in Australia.
Is it not then conceivable that this technology might be applied to humans? For example, Alan Westin discussed the possibility of "permanent implacements of 'tagging' devices on or in the body" as early as 1967.
If the technology were extended to humans, a myriad of identification-related applications could be envisaged such as the capability to find lost children or confused Alzheimer's patients, or to determine if job applicants are illegal immigrants or criminals.
The simplest form of the device would have a read-only character, similar to that now used in animals.
Even this most basic form would have numerous applications, for example, to identify Alzheimer's patients, children and the unconscious.
Implants about the size of a grain of rice have been a great boon for owners with lost or stolen pets.