"A philosophy has a practical power: it contributes to the changing of the world. This practical power has nothing to do with the engineering power that in the discussion above I attributed to sciences, including specific semiotics. A science can study either an animal species or the logic of road signals, without necessarily determining their transformation. There is a certain 'distance' between the descriptive stage and the decision, let us say, to improve a species through genetic engineering or to improve a signaling system by reducing or increasing the number of its pertinent elements. On the contrary, it was the philosophical position of the modern notion of thinking subject that led Western culture to think and to behave in terms of subjectivity. It was the position of notions such as class struggle and revolution that led people to behave in terms of class, and not only to make revolutions but also to decide, on the grounds of this philosophical concept, which social turmoils or riots of the past were or were not a revolution. Since a philosophy has this practical power, it cannot have a predictive power. It cannot predict what would happen if the world were as it described it. Its power is not the direct result of an act of engineering performed on the basis of a more or less neutral description of independent data."