Full Idea
General principles enter into our thoughts, serving as their inner core and their mortar. Even if we give no thought to them, they are necessary for thought, as muscles and tendons are for walking.
Gist of Idea
General principles, even if unconscious, are indispensable for thinking
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 1.01.20)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.84
A Reaction
Famously, Leibniz identified sufficient reason and non-contradiction as the two foundational principles. Modern logicians seem less keen on this idea, but then they have less interest in how we actually think.