How was the hypothetical character of theories of experiencethought about throughout the history of science? The essays cover periods from the middle ages to the 19th and 20th centuries. It is fascinating to see how natural scientists and philosophers were increasingly forced to realize that a natural science without hypotheses is not possible.

Depuis l'isolement de la creatine par CHEVREUL, en 1832, dans les extraits de viande (44) et son identification par LIEBIG, en r847, l'attention des biochimistes a porte principalement, pendant longtemps, sur le role de l'arginine dans la production de l'uree (I28), sur le cyde de l'ureo- genese (I34) et sur celui de la phosphocreatine (7I) et de la phospho- arginine (r68, I69) dans la contraction musculaire. A la suite de la mise en evidence, d'une part des reactions de trans- amidination expliquant la convertibilite entre l'arginine et un certain nombre de derives guanidiques (28,29,33,73,2 5, 29I, 292), et, d'autre part, du mecanisme complexe de la biosynthese de l'arginine (34, 45, 46, I95, I96) , l'importance du groupement guanidique dans la fixation et le transfert de l'azote organique est devenue beaucoup plus manifeste. Par ailleurs, l'isolement de nouvelles substances dont certaines: la phosphotaurocyamine, la phosphoglycocyamine (280-282), la phospho- 10mb ricine (270), jouent le meme role de phosphagenes que le creatine- et l'argininephosphate (257), amis en evidence la part importante que les derives guanidiques prennent dans la chimie du musde. L'etude de leur biogenese a montre en outre que leur role n'est pas seulement equivalent a l'arginine dans la fixation de l'azote du groupe amidinique, mais qu'ils sont capables de jouer egalement de role de regulateurs du metabolisme azote (258). I. Structure et formation.

Probability ideas are the success story common to the growth of the modern natural and social sciences. Chance, indeterminism, and statistical inference have radically and globally transformed the sciences in a "probabilistic revolution."This monumental work traces the rise, the transformation, and the diffusion of probabilistic and statistical thinking in the nineteenth and early twentieth centuries. It is less concerned with specific technical discoveries than with locating the probability revolution historically within a larger framework of ideas. There is no comparable study that treats the rise of probability and statistics in such scope and depth.The contributors - scientists, historians and philosophers from eight countries - make it possible for readers trained in many disciplines to see why the probabilistic revolution has been so complete and so successful, and how the rejection of uniform causality by quantum physics, the stochastic nature of evolutionary biology, the indeterminisms of human psychology, and the random processes of many economic activities are all manifestations of an underlying unifying concept.Volume 1 opens with provocative essays on scientific revolutions in general and the probabilistic revolution in particular by Thomas S. Kuhn, I. Bernard Cohen, and Ian Hacking. Other authors discuss the evolution of philosophical ideas about probability and their articulation and elaboration in the mathematics of the nineteenth century and describe the first applications of techniques of statistical inference during that century: Topics include the uses and abuses of official statistics by the bureaucrats of France, England, and Prussia; the use - or neglect - of statistics by nascent sociologists, demographers, and insurance actuaries; and the emergence of statistical methodologies in fields ranging from social reform to agricultural production.The emphasis in volume 2 is on the more recent scientific advances of the probabilistic approach in various natural and social sciences, from "random walks" in the stock market to random drift in natural selection, and from indeterminate events at the atomic level to unpredictable actions at the human level.Lorenz Kruger and Michael Heidelberger are philosophers of science at Gottingen University, Lorraine J. Daston is a historian at Brandeis University, Gerd Gigerenzer is a psychologist at the University of Constance, and Mary S. Morgan is an economist at York University. A Bradford Book."

Gustav Theodor Fechner (1801-1887) was a German physicist, psychologist, and philosopher, best known to historians of science as the founder of psychophysics, the experimental study of the relation between mental and physical processes. Michael Heidelberger's exhaustive exploration of Fechner's writings, in relation to current issues in the field, successfully reestablishes Fechner's place in the history and philosophy of science.