Markkula Center of Applied Ethics

What is Privacy?

By Michael McFarland, SJ
Definitions of Privacy

Privacy has many meanings. The most general is freedom from interference or intrusion, the right "to be let alone," a formulation cited by Louis Brandeis and Samuel Warren in their groundbreaking 1890 paper on privacy. 1 This recognizes that each person has a sphere of existence and activity that properly belongs to that individual alone, where he or she should be free of constraint, coercion, and even uninvited observation. As we would say today, each of us needs our own "space." Most would recognize the protected sphere to include personal opinions, personal communications, and how one behaves behind closed doors, at least as long as these do not lead to any significant threats to society. Many would also include behavior within the family and other intimate relationships in that sphere.

This broad concept of privacy has been given a more precise definition in the law. Since the Warren-Brandeis article, according to William Prosser, American common law has recognized four types of actions for which one can be sued in civil court for invasion of privacy.

They are, to quote Prosser:

  1. Intrusion upon the plaintiff's seclusion or solitude, or into his private affairs.
  2. Public disclosure of embarrassing private facts about the plaintiff.
  3. Publicity which places the plaintiff in a false light in the public eye.
  4. Appropriation, for the defendant's advantage, of the plaintiff's name or likeness. 2

The first category is the broadest and the hardest to interpret. "Intrusion" can mean physical presence, excessive telephone calls, and unauthorized observation, such as peering through windows of someone's home. It also covers cases where an authority forces someone to reveal personal information against that person's will, such as a court's unjustified demand that someone produce a broad array of personal records or an unnecessary requirement that someone take a blood test. 3

Another problem is defining what constitutes "private affairs." It is not an invasion of privacy, according to the courts at least, to follow someone on the street or to take a person's photograph in a public place. It would be, however, to do so unbidden in their home or a hospital room. 4 This category of privacy applies only to that part of a person's affairs that are not public and which the person does not wish to make public.

While the first of Prosser's categories can include attempts to influence, control or coerce someone's private affairs, most of the cases covered by this category and all of those covered by the other three involve the collection and/or use of personal information about someone. That is the core meaning of privacy. While some use the term more broadly to refer to any kind of uninvited interference with someone's personal life, privacy in the strict sense means shielding one's personal life from unwanted scrutiny.

Informational Privacy

It is this narrower meaning of privacy, which James H. Moor calls "informational privacy," 5 that concerns us here, because that is what is threatened by the information-processing capabilities of computers. Moor defines the right to informational privacy as "the right to control of access to personal information." This is a common definition in the literature, and one that we shall adopt here as well. The definition contains four important elements. First, it is about information. It focuses on the quest for knowledge about someone, rather than, say, physical proximity or constraint, or any other type of interference. Second, it refers to personal information. The knowledge intended gives some access to the subject's person, whether it is his or her identity, thoughts, aspirations, passions, habits, foibles or transgressions. Third, the issue is one of control. It is not how much or how little is known about the subject, but whether the subject can choose how much of the information is revealed and to whom. Finally, privacy is defined as a right. Within certain "domains," as More puts it, the person's control of personal information ought to be respected and protected.

Michael McFarland, S.J., a computer scientist with extensive liberal arts teaching experience and a special interest in the intersection of technology and ethics, served as the 31st president of the College of the Holy Cross.

June 2012


1. Samuel D. Warren and Louis D. Brandeis, "The Right to Privacy," Harvard Law Review, 4 (5), (1890): 193-220, p. 195, citing Judge Cooley in Cooley on Torts, 2nd ed.
2. William L. Prosser, "Privacy," California Law Review, 48 (1960): 338-423.
3. ibid.
4. ibid.
5. James H. Moor, "How to Invade and Protect Privacy with Computers," in Carol C. Gould (ed.), The Information Web: Ethical and Social Implications of Computer Networking, Boulder, CO: Westview Press (1989): 57-70.


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