It is important to be both a thinker and a doer and to have sense of responsibility. A theoretician who has no responsibility is withdrawn from the real world. His recommendations are made in a vacuum. Because he is not required to carry them out, they may be irresponsible and do harm. Similarly, those in charge - the doers - are often devoid of any real thought.
To find a purpose to life, on must be willing to act, to put excellence in one's work, and have concern for what is right ahead of personal safety. Life must be felt, not observed.