  Locke takes knowledge generally to consist in “the perception of the connexion and agreement, or disagreement and repugnancy of any of our Ideas” (E IV.i.1–2, p. 525), and among the three kinds of knowledge that he distinguishes, intuitive, demonstrative, and sensitive, the former two are kinds of certain knowledge. Intuitive and demonstrative knowledge differ in the number of intuitions involved, and consequently, differ in their degree of certainty (E IV.ii.14, pp.537–538). Intuitive knowledge is the most certain because the truth is grasped immediately. There are no intermediate steps, and doubt is impossible because the mind can no more avoid recognizing the truth than the open, functioning eye could avoid seeing light when turned toward the sun (E See IV.ii.1, p. 531). Demonstrative knowledge, though also qualifying as certain, is less so because it involves intermediate steps. We cannot grasp immediately that the three angles of any triangle are equal to two right triangles, and must instead construct the steps of a proof. Upon doing so, and upon grasping the connections between the steps of the proof, we have demonstrative knowledge (E IV.ii.2–3, p.531–532). Intuitive and demonstrative knowledge are forms of scientia, then. Locke defines that as “certain universal Knowledge”(E IV.iii.29, p. 559), and mere “particular matters of fact” (E IV.iii.25, pp. 555–56) do not qualify.