Only by reducing principles can they be understood and related to each other. Ultimately, from a high "vantage point" (47) the philosopher can then view the vast labyrinth of sciences and the arts. d'Alembert then goes on to describe the tree of knowledge and the separation and simultaneous connections between memory, reason, and imagination.
The idea that understanding requires simplification is central to this passage. The philosopher's high vantage point allows them to see the interconnectedness of all sciences and arts. d'Alembert uses the metaphor of a tree of knowledge to illustrate how memory, reason, and imagination are connected.