As early as 1913, Husserl in Ideen zu einer reinen Phänomenologie und phänomenologischen Philosophie designated a descriptive and analytical study of the world of common experience or — as it has come to be denoted in the terminology of his later writings — the life-world (Lebenswelt) as an urgent desideratum. What is meant is the world as encountered in everyday life and given in direct and immediate experience, especially perceptual experience and its derivatives like memory, expectation, and the like, independently of and prior to scientific interpretation. At every moment of our life, we find ourselves in the world of common everyday experience; with this world we have a certain familiarity not derived from what science might teach us; within that world we pursue all our goals and carry on all our activities, including scientific ones. As the universal scene of our life, the soil, so to speak, upon which all human activities, productions, and creations take place, the world of common experience proves the foundation of the latter as well as of whatever might result from them. As far as the construction of the scientific universe as well as the elaboration of a science in the specific modern, "Galilean", style is concerned, the perceptual world underlies it and is presupposed by it in a still further sense, in that it serves as a point both of departure and of reference for that construction which is to provide an explanation in mathematical terms of events and occurrences in the world of perceptual experience.