What connections does the author draw between the Black Death and the shift of power in Europe?

The first impact of the plague was, therefore, demographic. The lives they took in just seven years would take two centuries to recover, while the survivors would reorganize in a different way. During the epidemic years, the rural population had moved to the cities in search of food and company, and given the large number of vacancies left by the plague, they no longer had to return. The countryside was depopulated, while life in the cities was revitalized, driven by the concentration of fortunes that followed the high mortality. The old rural aristocracy, accustomed to living comfortably on incomes, finds two possibilities: lease their land at lower prices or exploit them directly, hiring producers and paying them higher and higher days. The stately power lost, therefore, part of its purchasing power, while the day laborers, regretful valuable due to their shortage, increased their well-being.

The shortage of arms and the rise of the bourgeoisie were decisive for the development of the technique, one of the hallmarks of the Renaissance, closely linked to the parallel advancement of science. Machines reduce the amount of force and work needed, and appear to serve a particular class, the bourgeoisie, which finds in them a concrete response to their needs. In the technical ascent an essential change of mentality prevails, since the manual work - the mechanical arts - was despised during the Middle Ages. Leonardo da Vinci claims it when he says: "In my opinion, the sciences that have not been born of experience, mother of all certainty, and that do not end in a definite experience, are vain and full of errors." Science and technique go hand in hand, and good proof of this are the calculations of the architect and sculptor Filippo Brunelleschi, prior to the construction of the dome of Santa María del Fiore, in Florence.