Editing Kenneth Arrow (section)

===Arrow's impossibility theorem===
{{Main|Arrow's impossibility theorem}}
Arrow's monograph ''[[Social Choice and Individual Values]]'' derives from his 1951 [[Doctor of Philosophy|PhD]] thesis.

{{Blockquote|If we exclude the possibility of interpersonal comparisons of utility, then the only methods of passing from individual tastes to social preferences which will be satisfactory and which will be defined for a wide range of sets of individual orderings are either imposed or dictatorial.<ref>{{cite journal |last1=Arrow |first1=Kenneth J. |title=A Difficulty in the Concept of Social Welfare |journal=Journal of Political Economy |date=1950 |volume=58 |issue=4 |pages=328–346 |doi=10.1086/256963 |jstor=1828886 |s2cid=13923619 |url=https://www.jstor.org/stable/1828886 |issn=0022-3808}}</ref>}}

In what he named the General Impossibility Theorem, he theorized that, unless we accept to compare the levels of utility reached by different individuals, it is impossible to formulate a social preference ordering that satisfies all of the following conditions:<ref name=theo/>

# '''Nondictatorship''': The preferences of an individual should not become the group ranking without considering the preferences of others.
# '''Individual Sovereignty''': each individual should be able to order the choices in any way and indicate ties
# '''Unanimity''': If every individual prefers one choice to another, then the group ranking should do the same
# '''Freedom From Irrelevant Alternatives''': If a choice is removed, then the others' order should not change
# '''Uniqueness of Group Rank''': The method should yield the same result whenever applied to a set of preferences.  The group ranking should be transitive.

The theorem has implications for [[welfare economics]] and theories of [[justice]], and for voting theory (it extends the [[Condorcet paradox]]). Following Arrow's logical framework, [[Amartya Sen]] formulated the [[liberal paradox]] which argued that given a status of "Minimal Liberty" there was no way to obtain [[Pareto optimality]], nor to avoid the problem of social choice of neutral but unequal results.<ref name=theo>{{cite web|last1=Morreau|first1=Michael|title=Arrow's Theorem|url=https://plato.stanford.edu/entries/arrows-theorem/|website=The Stanford Encyclopedia of Philosophy|publisher=Metaphysics Research Lab, Stanford University|access-date=25 February 2017|date=1 January 2016}}</ref>