After this, I investigated what is essential for a proposition to be true and certain. Since I had found one proposition that I knew was true, I believed I should be able to find the basis for this certainty as well.
It was 9 P.M. before we reached our camp on Vashon’s Island12. The Narrows were quite alive with Indians fishing for small fish and salmon. They trolled for the salmon and caught the small fish with a species of rake, composed of sharp nails set like teeth into a paddle. This instrument served at once to direct the canoe, and in cutting into the water to pass through shoals of small fish, transfixing them to the nails. It was then brought against the side of the boat behind the fisherman with a jar, so as to loosen the catch and prepare for another load. We purchased fish and clams from the Indians for our table.
After this I inquired in general into what is essential to the truth and certainty of a proposition; for since I had discovered one which I knew to be true, I thought that I must likewise be able to discover the ground of this certitude.