You know more of a road by having traveled it than by all the conjectures and descriptions in the world.
— William Hazlitt

There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
Mark Twain conjecture quote

When the mariner has been tossed for many days in thick weather, and on an unknown sea, he naturally avails himself of the first pause in the storm, the earliest glance of the sun, to take his latitude, and ascertain how far the elements have driven him from his true course. Let us imitate this prudence, and, before we float farther on the waves of this debate, refer to the point from which we departed, that we may at least be able to conjecture where we now are.
— Daniel Webster

This place is the Devil, or at least his principal residence, they call it the University, but any other appellation would have suited it much better, for study is the last pursuit of the society; the Master eats, drinks, and sleeps, the Fellows drink, dispute and pun, the employments of the undergraduates you will probably conjecture without my description.
— Lord Byron

From man or angel the great Architect did wisely to conceal, and not divulge his secrets to be scanned by them who ought rather admire; or if they list to try conjecture, he his fabric of the heavens left to their disputes, perhaps to move his laughter at their quaint opinions wide hereafter, when they come to model heaven calculate the stars, how they will wield the mighty frame, how build, unbuild, contrive to save appearances, how gird the sphere with centric and eccentric scribbled o'er, and epicycle, orb in orb.
— conjecture quotation by John Milton