What is life, and where does it come from? The question is very old, but it reemerged in the seventeenth century with the crisis of the Aristotelian-Galenic paradigm. Matter was now stripped of any impulse and capacity for self-organization; therefore, it was necessary to find something that would take into account the strength and information that it seemed to hold, especially in what were considered vital phenomena. Georg Ernst Stahl and Friedrich Hoffmann, both professors in Halle and responsible for two (...) of the most famous medical systems of the first half of the eighteenth century, offered solutions to the problem that only appear to be very different. The first invoked the soul as an ideal place of production of the energy that allowed the human body to fight the putrefactive forces in the natural world; the second referred to the concept of ether, to which he attributed modes of action basically similar to those that tradition attributed to vegetative and sensitive souls. This paper highlights the positions of the two physicians, setting them in the climate of the revisitation of ancient certainties that characterized natural philosophy in the seventeenth and eighteenth centuries. (shrink)