<P> Galileo Galilei built his rejection of Aristotle's law of gravity on a case study selected by information - oriented sampling and not by random sampling . The rejection consisted primarily of a conceptual experiment and later on a practical one . These experiments, with the benefit of hindsight, seem self - evident . Nevertheless, Aristotle's incorrect view of gravity had dominated scientific inquiry for nearly two thousand years before it was falsified . In his experimental thinking, Galileo reasoned as follows: if two objects with the same weight are released from the same height at the same time, they will hit the ground simultaneously, having fallen at the same speed . If the two objects are then stuck together into one, this object will have double the weight and will according to the Aristotelian view therefore fall faster than the two individual objects . This conclusion seemed contradictory to Galileo . The only way to avoid the contradiction was to eliminate weight as a determinant factor for acceleration in free fall . Galileo's experimentalism did not involve a large random sample of trials of objects falling from a wide range of randomly selected heights under varying wind conditions, and so on . Rather, it was a matter of a single experiment, that is, a case study . </P> <P> Galileo's view continued to be subjected to doubt, however, and the Aristotelian view was not finally rejected until half a century later, with the invention of the air pump . The air pump made it possible to conduct the ultimate experiment, known by every pupil, whereby a coin or a piece of lead inside a vacuum tube falls with the same speed as a feather . After this experiment, Aristotle's view could be maintained no longer . What is especially worth noting, however, is that the matter was settled by an individual case due to the clever choice of the extremes of metal and feather . One might call it a critical case, for if Galileo's thesis held for these materials, it could be expected to be valid for all or a large range of materials . Random and large samples were at no time part of the picture . However it was Galileo's view that was the subject of doubt as it was not reasonable enough to be the Aristotelian view . By selecting cases strategically in this manner one may arrive at case studies that allow generalization . </P> <P> It is generally believed that Frederic Le Play first introduced the case - study method into social science in 1829 as a handmaiden to statistics in his studies of family budgets . </P> <P> Other roots stem from the early 20th century, when researchers working in the disciplines of sociology, psychology, and anthropology began making case studies . In all these disciplines, case studies were an occasion for postulating new theories, as in the grounded - theory work of sociologists Barney Glaser (1930 -) and Anselm Strauss (1916 - 1996). </P>

Who has used the case study method for first time