A small treatise on philosophical theology, and not strictly biblical, this is how Kant presented his work to the theologian Matern Reuss in 1793. This work deals with natural religion as conceived by the philosopher Konisgberg, that is to say a religion above all rational and reasonable. Its object is in fact the faith of man which is based solely on reason: a faith in which every man could and should rediscover, by his own means, the unconditional moral principles which must direct his free action. Practical teaching and not science of the divine, traditional and unrevealed belief - but which neither condemns nor contradicts all revelation - religion thus reduced to the limits of simple reason stands above all against superstition and enthusiasm, as a truly universal spirituality.