Most undergraduates are likely to become acquainted with John Stuart Mill's famous harm principle at some point.  Here is how he stated the principle in On Liberty:

The
object of this Essay is to assert one very simple principle, as
entitled to govern absolutely the dealings of society with the
individual in the way of compulsion and control, whether the means used
be physical force in the form of legal penalties, or the moral coercion
of public opinion. That principle is, that the sole end for which
mankind are warranted, individually or collectively, in interfering
with the liberty of action of any of their number, is self-protection. That
the only purpose for which power can be rightfully exercised over any
member of a civilized community, against his will, is to prevent harm
to others. His own good, either physical or moral, is not
sufficient warrant. He cannot rightfully be compelled to do or forbear
because it will be better for him to do so, because it will make him
happier, because, in the opinion of others, to do so would be wise, or
even right… The only part of the conduct of anyone, for which he is
amenable to society, is that which concerns others. In the part which
merely concerns himself, his independence is, of right, absolute. Over
himself, over his own body and mind, the individual is sovereign.

The harm principle is itself a fascinating topic (perhaps for another Lexicon entry), but on this occasion, we are using it to ask the question: what constitutes harm to others? 
Of course, we can all enumerated examples of harm.  Alice kicks Ben in
the shin and bruises him.  Carla steals David's lunch.  Edwina falsely
accuses Frank of plagarism.  But all of these examples assume that we
can distinguish what the infliction of harm from something else–the
denial of a privilege or advantage.  Gertrude denies Harry a job. 
Ingrid decides not to invite Jim to her party.  Karl refuses to share
his collection of MP3 files with Laurie.  Are these harms or not?

The problem of distinguishing harm from denial of
advantage or rights from privileges involves one of the most
interesting concepts in legal theory–the notion of a baseline.  This entry in the Legal Theory Lexicon introduces to the baseline problem.  As always, the Lexicon is aimed at law students, especially first-year students, with an interest in legal theory.

The Function of a Baseline

A variety of important legal concepts are relative in the following
sense: an action, event, or state of affairs falls under the concept by
comparison to some alternative.  Mill's idea of "harm" has this
property: an event is a "harming" only in comparison to some prior or
alternative state of affairs.  A similar point could be made about
"injury," "advantage," "benefit," and similar terms.

There is where the notion of a baseline comes in.  For example, we might use a temporal baseline to define harm: action X is a harm to individual P if and only if P is worse off after X and this change in welfare is causally produced by X.  This
sounds plausible, but it isn't difficult to cook up examples where this
formula doesn't match our intuitive understanding of harm.  Mary asks
Nancy to repay a $10 loan, and Nancy agrees to do so. Nancy is worse
off, but it isn't clear that Mary has harmed Nancy–even though her
request for payment is the cause of Nancy's being worse off
(financially) than she was before the request for repayment. A similar
point could be made about advantage. Mary forgives Nancy’s debt.
Nancy's financial circumstances aren't improved relative to a temporal
baseline, but we might believe that Mary has conferred an advantage on
Nancy. In both examples, the temporal baseline doesn't capture our
intuitive sense that the relevant baseline ought to be defined in terms
of Mary and Nancy's respective entitlements.

Possible Legal Baselines

So how could the law identify baselines?  Let's just list a few possibilities:

Positive
Entitlements: The law could take one's existing entitlements (as
defined by the positive law) as the baseline for measuring legal harm
or advantage.

Common law: Another option would be to take the common law system of
property, contract, and tort law as the definition of baseline
entitlements.  Official actions that worsened an individual's position
relative to the common-law baseline could be defined as harms, and
actions that bettered the common-law baseline could be defined as
advantages.

Natural rights: Yet another possibility would be the the baseline
could be defined by a theory of natural rights.  One such theory is
offered by theories of the state of nature and the social contract. 
The baseline of natural rights could be identified with those rights
that would be retained by rational individuals who agreed to enter into
civil society from a state of nature.

Human rights: Another source of a baseline might be the bundle of entitlements identified by international human rights law.

At this point, I'm sure that Lexicon
readers will have recognized that the identification of a baseline can
be crucially important to answering the question whether an injury has
occurred.  If positive law identifies the baseline, then there are no
injuries unless a legal entitlement is violated.  But if natural right
sets the baseline, then there can be injury without violation of the
positive law.

Contexts in which Baselines Matter

Baselines are important in a variety of contexts.  How do we distinguish offers from threats? 
Nozick's clever distinction is that a threat is an offer you would
rather not receive, but underlying his point is the notion of a
baseline.

Baselines have played an especially prominent role in constitutional
theory.  In that context, the baseline problem is strongly associated
with Cass Sunstein, and especially with his analysis of the United
States Supreme Court's decision in Lochner v. New York.  As most readers of the Lexicon
will know, the Supreme Court invalidated a New York statute that
regulated the number of hours that could be worked by bakers on the
basis of the due process clause of the 14th Amendment of the United
States Constitution.  The statute was challenged on the basis that it
deprived bakery owners of liberty.  The question is what determines the
baseline.  Sustein argued that the Court had erroneously assumed that
the common-law provides a natural baseline, when in fact the system of
common-law rights is itself a product of positive law and hence subject
to redefinition by legislative action.  The following passage provides
the flavor of Sunstein's argument:

The
Lochner Court required government neutrality and was skeptical of
government “intervention”; it defined both notions in terms of whether
the state had threatened to alter the common law distribution of
entitlements and wealth, which was taken to be a part of nature rather
than a legal construct. Once the common law system came to be seen as a
product of legal rules, the baseline from which constitutional
decisions were made had to shift. When the Lochner framework was
abandoned in West Coast Hotel, the common law system itself appeared to
be a subsidy to employers. The West Coast Hotel Court thus adopted an
alternative baseline and rejected Lochner era understandings of
neutrality and action. (Sunstein, Lochner's Legacy, p. 917)

Of
course, the system of common-law rights could be used as a baseline. 
Sunstein's point is that the common-law is not more "natural" than any
other baseline derived from the positive law.

One can imagine a variety of replies to Sunstein's argument.  One
possibility is to argue that the common-law system of rights does have
some special statues.  For example, it might be argued that common-law
property, contract, and tort rights instantiate a system of natural
rights.  Or it might be argued that the common law reflects deeply held
and wide shared social norms that provide the content of a shared
social sense of justice.  Whether arguments like this will succeed on
the merits is certainly contestable, but for your purpose the important
point is that baselines must be justified–they cannot just be assumed.

Conclusion

Concepts like harm, injury, advantage, and benefit are pervasive in
legal theory.  Understanding these concepts requires an appreciation of
the baseline problem.  The pont of this Lexicon entry is to
give the reader a basic understanding of what baselines are and how
they can be challenged and defended.  Of course, there is much more to
be said, and the bibliograph provides some additional sources to
investigate.

Bibliography

Jack M. Beerman & Joseph William Singer, Baseline Questions in Legal Reasoning: The Example of Property in Jobs, 23 Ga. L. Rev. 911 (1989).

David E. Bernstein, Lochner's Legaacy's Legacy, 82 Tex. L. Rev. 1 (2003).

Cass Sunstein, Lochner's Legacy, 87 Colum. L. Rev. 873 (1987).

Cass Sunstein, After the Rights Revolution: Civil Rights, Environmental Law, and Statutory Interpretation (Harvard University Press 1990).

(This entry was last revised on March 1, 2009. My thanks to Kenneth Simons for his comments.)

Source: Lawrence Solum