It is clear that there is no classification of the Universe that is not arbitrary and full of conjectures. The reason for this is very simple: we do not know what kind of thing the universe is.
You should look at all the experimental information at hand, not only the most relevant, and be prepared to make conjectures if that helps.
You know more of a road by having travelled it then by all the conjectures and descriptions in the world.william hazlitt
All doctrines relating to the creation of the world, the government of man by superior beings, and his destiny after death, are conjectures which have been given out as facts, handed down with many adornments by tradition, and accepted by posterity as "revealed religion". They are theories more or less rational which uncivilised men have devised in order to explain the facts of life, and which civilised men believe that they believe.william winwood reade
Trained in a less severe school than that of geometry and physics, his reasonings are almost always loose and inconclusive. His generalizations seem to have been reached before he had obtained the materials upon which he rests them: His facts, though frequently new and interesting, are often little more than conjectures; and the grand phenomena of the world of life, and instinct, and reason, which other minds have woven into noble and elevating truths, have thus become in Mr. Darwin's hands the basis of a dangerous and degrading speculation.david brewster
When we look to presumed sources of origin for competing evolutionary explanations of the giraffe's long neck, we find either nothing at all, or only the shortest of speculative conjectures. Length, of course, need not correspond with importance. Garrulous old Polonius , in a rare moment of clarity, reminded us that "brevity is the soul of wit" (and then immediately vitiated his wise observation with a flood of woolly words about Hamlet 's Madness.)stephen jay gould
Whenever a time comes that the justice overwhelms and overcomes cruelty, it is prohibited to form negative conjectures and opinions about anyone, except when one knows it about him. But whenever a time comes that cruelty and oppression overwhelms the (quantum of) justice, then one must not have good opinions about the beneficence of a person, till such time he knows it(for sure).