Can some one tell me what this means? (John S. Mill)?

... As it is useful ... As it is useful that while mankind are imperfect there should different experiments of living that free scope should be given to varieties of character short of injury to others and that the worth of different modes of life should be proved practically, when any one thinks fit to try them. It is desirable, in short, that in things which do not primarily concern others, individuality should ert it self….