Each problem that I solved became a rule, which served afterwards to solve other problems.

The line captures Descartes’ methodological ambition: to turn successful acts of reasoning into reusable procedures. Rather than treating solutions as isolated feats, he frames them as steps toward a general method—rules that can be applied to new questions. This reflects the early modern push to systematize knowledge (especially in mathematics and natural philosophy) by extracting general principles from particular cases. The quote also suggests an iterative, cumulative view of inquiry: progress comes from reflecting on how one solved a problem, then codifying that approach so future problems become more tractable. In spirit, it anticipates later ideas about algorithms, heuristics, and the transfer of problem-solving strategies across domains.