"Since everything that lives is obliged to expend and receive life, there is an exchange of modifications between the living creature and its environment. And yet, once that vital necessity is satisfied, our species—a positively strange species—thinks it must create for itself other needs and tasks besides that of preserving life. … Whatever may be the origin or cause of this curious deviation, the human species is engaged in an immense adventure, an adventure whose objective and end it does not know. … The same senses, the same muscles, the same limbs—more, the same types of signs, the same instruments of exchange, the same languages, the same modes of logic—enter into the most indispensable acts of our lives, as they figure into the most gratuitous. ... In short, man has not two sets of tools, he has only one, and this one set must serve him for the preservation of his life and his physiological rhythm, and expend itself at other times on illusions and on the labours of our great adventure. ... The same muscles and nerves produce walking as well as dancing, exactly as our linguistic faculty enables us to express our needs and ideas, while the same words and forms can be combined to produce works of poetry. A single mechanism is employed in both cases for two entirely different purposes."