For these reasons, as soon as my age permitted me to pass from under the control of my instructors, I entirely abandoned the study of letters, and re… - René Descartes

I entirely abandoned the study of letters. Resolving to seek no knowledge other than that of which could be found in myself or else in the great book of the world, I spent the rest of my youth traveling, visiting courts and armies, mixing with people of diverse temperaments and ranks, gathering various experiences, testing myself in the situations which fortune offered me, and at all times reflecting upon whatever came my way so as to derive some profit from it.

I took especially great pleasure in mathematics because of the certainty and the evidence of its arguments.

Divide each difficulty into as many parts as is feasible and necessary to resolve it.

Pues tales frutos he recogido ya de ese método, que, aun cuando, en el juicio que sobre mí mismo hago, procuro siempre inclinarme del lado de la desconfianza mejor que del de la presunción, y aunque, al mirar con ánimo filosófico las distintas acciones y empresas de los hombres, no hallo casi ninguna que no me parezca vana e inútil