The view is often defended that sciences should be built up on clear and sharply defined basal concepts. In actual fact no science, not even the most exact, begins with such definitions. The true beginning of scientific activity consists rather in describing phenomena and then in proceeding to group, classify and correlate them.
Sigmund FreudMy boy! Smoking is one of the greatest and cheapest enjoyments in life, and if you decide in advance not to smoke, i can only feel sorry for you.
Sigmund FreudInstinct of love toward an object demands a mastery to obtain it, and if a person feels they can't control the object or feel threatened by it, they act negatively toward it.
Sigmund Freud