The occasion for Kant's cosmogenetic enterprise was first a discovery made by Maupertuis in the Discourse on the figure of the stars. The purpose of this treatise was to present the main arguments in the opposition between Descartes and Newton, but he mentions in passing the observation of unknown "nebular formations" close to well-known stars, and observed thanks to progress in optics. Maupertuis thought they were massive stars, but Kant had reservations about this interpretation: if these nebulae were indeed stars, their luminous radiation should be proportional to their size, which is clearly not the case.

So Kant suggested instead that they were clusters of stars. And he compared this hypothesis with another proposed by Thomas Wright in his book An Original Theory or New Hypothesis o f t h e U n i v e r s e , b a s e d o n h i s observations of the Milky Way. For him, the Milky Way should be interpreted as the distribution of a myriad of stars in a single plane . From this, Kant deduced that the spherical nebulae we observe in the sky are the total form of what he called island-universes , galaxies of stars distributed in a circle on the same rotating plane, of which the Milky Way is the external mark that we see insofar as we are inside in one of them. What we really see is the slice of the disc that includes us. These are the first drawings of galaxies imagined by Thomas Wright and, a little later, the

s major contribution, he went on to imagine another type of nebula, more ancient, more primordial, in order to envisage what the world was like in its initial state, and to finally respond to the impasse in which Descartes and Newton had left us. This primordial nebula is not made up of a cluster of stars, but of a cluster of particles that are at the origin of stellar and planetary systems. This is how the moment of cosmogenesis properly begins.

The definition of these primitive particles that form a cloud of dust should lead us to ask : what theory of matter Kant is working from, in this text. In the preface, he had taken for himself a quotation that the Enlightenment had was in the habit of using to refer to the Cartesian cosmological gesture: Give me matter and I will make a world of it . However, the Theory of the Heaven cannot be said to pose the question of the essence of matter, as the Physical monadology published the following year will do. It's all in the formula: Give me matter and I will make a world of it > matter is given at the beginning. But even if the study of cosmology is not the study of particle physics, it cannot fail to produce differentiation in the matter with which it begins, in order to break up the uniformity. (So any cosmology will have even a minimal theory of the elements to introduce symmetry breaks and provoke motion. Indeed, if all the elements in the universe were