Some have conjectured that the distant planet could sustain life.
We only conjecture about his motives.
It is fashionable now to conjecture that the Big Bang was caused by a random quantum fluctuation in a vacuum devoid of space and time. —Martin Gardner, Skeptical Inquirer, November/December 1998
… their traces left for future archaeologists to rediscover and perhaps to wonder or conjecture over. —Jane Jacobs, Cities and the Wealth of Nations, 1984
I am anxious to conjecture beforehand what may be expected from the sowing turneps [sic] in jaded ground, how much from the acre, & how large they will be? —Thomas Jefferson, letter, 29 Dec. 1794
Despairing of assistance and protection from below (as they foolishly conjecture) they talk of capitulating and coming upon terms with the French and Indians … —George Washington, 24 Apr. 1776, in The Papers of George Washington, 1984