Karl Popper, answered from the texts and cited to the page.
The closed society is, at its core, the tribal or clan society — the form of human association in which individuals are not confronted with personal decisions but are instead held within a semi-organic framework of kinship, shared danger, shared joy, and shared distress.1 It resembles a herd or tribe whose members are bound not by abstract social relationships such as division of labour, but by concrete physical relationships: touch, smell, sight.2
Its laws are not based on rational reflection or accountability but on magical ideas — taboos, the appeasement of fate — which are simply accepted, not questioned.3 The distinction I draw between the closed and the open society is precisely the distinction between a world governed by taboo and a world in which rational reflection upon social arrangements becomes possible.4
In the open society, individuals recognize personal responsibility; they can examine legislation, weigh consequences, and make decisions based on conscious preference rather than inherited ritual. What gives the concept its urgency is not merely the description of primitive societies. The breakdown of the closed society — when the tribe dissolves, when the individual suddenly becomes, as it were, homeless in the social sense — produces a reaction.5
That reaction is what I call the Strain of Civilization: the longing for the lost unity of the tribe, expressed as historicism (the prophet who promises a millennium), collectivism (the communion of the lost tribe), and irrationalism (the community of the elect).6 Both Plato's Republic and Hitler's movement were, sociologically speaking, responses to this same strain — attempts to arrest society, to re-introduce by force a closed order.7
But an artificially closed society can never be what the natural closed society was; it must contain evils the primitive tribe did not know, precisely because its members have already eaten from the tree of knowledge and cannot return to tribal innocence.8 The return to the closed society, dressed in the language of organic wholeness or mystical community, is what I call the return to the cage.9
Those who resist that pull — who carry what I describe as the cross of being human, who do not flinch from social change but try to make the best of it — are the fighters for the open society.10
A closed society resembles a herd or a tribe in being a semi-organic unit whose members are held together by semi-biological ties—kinship, living together, sharing common efforts, common dangers, common joys and common distress.The Open Society and Its Enemies, p. 204
It is still a concrete group of concrete individuals, related to one another not merely by such abstract social relationships as division of labour and exchange of commodities, but by concrete physical relationships such as touch, smell, and sight.The Open Society and Its Enemies, p. 204
They are not based upon a principle of reasonable accountability, but rather upon magical ideas, such as the idea of appeasing the powers of fate.The Open Society and Its Enemies, p. 204
In what follows, the magical or tribal or collectivist society will also be called the closed society, and the society in which individuals are confronted with personal decisions, the open society.The Open Society and Its Enemies, p. 204
When this closed society breaks down, or opens up, when the individual suddenly becomes homeless in the social sense, then a reaction sets in.After The Open Society, pp. 176–178
The three enemies are reactions to the breakdown of the tribal society: (a) Historicism (historical prophecy - the prophet, the leader - the prophesied paradise, the millennium, Utopia) (b) Collectivism (the communion, the lost tribe) (c) Irrationalism (the community of the elect)After The Open Society, pp. 176–178
Both Plato and Hitler were exponents of a reaction to the same social phenomenon: social change. Both represented an attempt to get over the strain caused by the breakdown of the closed society, both are exponents of The Strain of Civilization, and of The Fear of Change.After The Open Society, pp. 176–178
It is clear that, once we have eaten from the tree of knowledge, once we have realized that tribal taboos are man-made, we can never return to the innocence of the 'natural' closed society. The 'artificially' closed society, the arrested society, must contain many evils which the 'natural' closed society did not know.After The Open Society, pp. 176–178
the return to the closed society which they advocate is the return to the cage, and to the beasts.The Open Society and Its Enemies, p. 471
to carry the cross of being human; not to flinch from the strain of civilization; not to get hysterical about social change; but to try to make the best of it. Those who try are the fighters for the 'Open Society'.After The Open Society, pp. 135–136