Definition of "uncertain"

Man, without the protection of a superior Being, […] is […] uncertain of everything that he hopes for.

1664, John Tillotson, “Sermon I. The Wisdom of Being Religious. Job XXVIII. 28.”, in The Works of the Most Reverend Dr. John Tillotson, Late Lord Archbishop of Canterbury: , published 1720

Turning back, then, toward the basement staircase, she began to grope her way through blinding darkness, but had taken only a few uncertain steps when, of a sudden, she stopped short and for a little stood like a stricken thing, quite motionless save that she quaked to her very marrow in the grasp of a great and enervating fear.

1914, Louis Joseph Vance, chapter III, in Nobody, New York, N.Y.: George H[enry] Doran Company, published 1915

O woman! in our hours of ease, / Uncertain, coy, and hard to please!

1808 February 22, Walter Scott, “(please specify the introduction or canto number, or chapter name)”, in Marmion; a Tale of Flodden Field, Edinburgh: […] J[ames] Ballantyne and Co. for Archibald Constable and Company, […]; London: William Miller, and John Murray

Thinking about the uncertain refines our perception of the certain, and generally this takes place in a framework in which the uncertain is the future and the certain is the present.

2011, John Lyons, The Phantom of Chance: From Fortune to Randomness in Seventeenth-Century French Literature‎