Roughly speaking, the goods of which private possession is possible are material, whereas the other sort of goods are mental. Material goods, if the supply is not unlimited, should be distributed on principles of justice: no one should have too much if, in consequence, someone else has too little. ... But mental goods such as knowledge, enjoyment of beauty, friendship and love are not taken away from other people by those whose lives are enriched by them. There is not, therefore, any prima-facie case for restrictions of liberty in this sphere.
Source: Bertrand Russell: John Stuart Mill，1955.
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