But those who dare to fall in love with practice without science, or with science without practice, are like the sailor who steers a vessel with neither rudder nor compass and no idea of where to go.

The idea is a vessel. Science is the compass. Skill is the rudder. But those who dare to fall in love with practice without science, or with science without practice, are like the sailor who steers a vessel with neither rudder nor compass and no idea of where to go.