Although the first few years of an intellectual life seem by far the most fruitful, in which each one of them seems to bring about a complete transformation in knowledge, after a certain time, although progress seems to lose momentum, the gain in direction is remarkable. In other words: at the beginning, when everything is new, we discover a lot, but knowledge expands simultaneously in many directions, and we can hardly see a direction, we can hardly see where the effort will lead. After a few years, we make far fewer mistakes, and although the difficulties increase, we move forward more consciously towards where we want to be.