The word detny is coming from the Russian root word deti (children). It was used to differentiate people with children from people without children mainly for tax benefits. But in this book the author describes that special emotional state of having children when people become responsible for the way they live, think and behave. For example a detny man can’t despair, or become lazy because children watch.
Not all people who have children are in the detny condition. They look at children as objects for teaching, for instance to say “thank you” or “please.”
“It is easy to recognize the detny man: children are interesting to him,” S.Soloveychik says.