[The possible use of sociological onsets in theory on the problem of age and surroundings (author's transl)].

The possibility of using sociological theories on practical problems is a main view point for judging their usefulness. From a scientific-theoretical point of view activity- and disengagement-theory are adequately examined in this contribution. By this it is shown that these theories are lacking mainly in precision and consistency; moreover there is a limitation concerning their relevancy for daily use by the lack of the possibility of producing the variables used in the onsets.