
If all men were well off, if poverty and disease had been reduced to their lowest possible point, there would still remain much to be done to produce a valuable society; and even in the existing world the goods of the mind are at least as important as the goods of the body…
But it cannot be maintained that philosophy has had any very great measure of success in its attempts to provide definite answers to its questions… as soon as definite knowledge concerning any subject becomes possible, this subject ceases to be called philosophy, and becomes a separate science. The whole study of the heavens, which now belongs to astronomy, was once included in philosophy; Newton's great work was called 'the mathematical principles of natural philosophy'. Similarly, the study of the human mind, which was a part of philosophy, has now been separated from philosophy and has become the science of psychology.
For Russell (1912: 90) “to a great extent, the uncertainty of philosophy is more apparent than real.” When philosophical questions are resolved they are no longer in the philosophical realm; “while those only to which, at present, no definite answer can be given, remain to form the residue which is called philosophy." But philosophy is more than process or residue:
There are many questions -- and among them those that are of the profoundest interest to our spiritual life -- which, so far as we can see, must remain insoluble to the human intellect unless its powers become of quite a different order from what they are now. Has the universe any unity of plan or purpose, or is it a fortuitous concourse of atoms? Is consciousness a permanent part of the universe, giving hope of indefinite growth in wisdom, or is it a transitory accident on a small planet on which life must ultimately become impossible?
For Russell !912: 92) "[t]he value of philosophy is, in fact, to be sought largely in its very uncertainty":
The man who has no tincture of philosophy goes through life imprisoned in the prejudices derived from common sense, from the habitual beliefs of his age or his nation, and from convictions which have grown up in his mind without the co-operation or consent of his deliberate reason. To such a man the world tends to become definite, finite, obvious; common objects rouse no questions, and unfamiliar possibilities are contemptuously rejected.
From The Value of Philosophy, Chapter 15 of Betrand Russell's 1912 volume, The Problems of Philosophy, Oxford University Press.

British Philosopher and Logician [1872-1970]
All that has been learned empirically about evolution in general and mental processes in particular suggests that the brain is a machine assembled not to understand itself, but to survive. Because these two ends are basically different, the mind unaided by factual knowledge from science sees the world only in pieces. It throws a spotlight on those portions of the world it must know in order to live until the next day, and surrenders the rest to darkness.
Wilson maintains that “myth and self-deception, tribal identity and ritual” provided “the adaptive edge” historically rather than aspiring to the “objective truth.” Wilson’s parting shot is the notion that:
The ships that brought us here are to be left scuttled and burning at the shore
Wilson, E. O. (1999) Consilience. Random House New York
Why is there something rather than nothing?
What is the nature of time?
Does the universe have an ultimate purpose or meaning?
Naturally, we will continue to grapple with these, and other, very big questions; but their final resolution may be forever beyond the grasp of mere human intellect and ingenuity.

Uncertainty is at the heart of philosophical questions. Some very powerful, set-piece, critical thinking tools have emerged from Western philosophical quest. We can utilize Plato's cave allegory, Aristotle's golden mean, Occam, razor, Descartes' pernicious demon and method of radical doubt, Kant's categorical imperative, Darwin's natural selection, Wittgenstein's family resemblances, Gadamer's prejudices, Ricouer's mimesis, Kuhn's paradigm shift, Popper's falsifiability, Berlin's pluralism and Rawls' veil of ignorance, without necessarily agreeing with any of the original conclusions.
Strictly speaking, philosophy is not useful. As soon as reliable knowledge is gained in a subject area it can no longer be called philosophy. Historically, cosmology and psychology were aspects of philosophy.
Frontiers of scientific knowledge—for example: the nature of the very early universe, the emergence of membrane-bound, fully-metabolizing prokaryotic cells from macromolecules, and the neuronal basis for language and consciousness—remain partially in the realm of philosophical speculation.
Ludwig Wittgenstein famously stressed that in philosophy the process—the arguing and analyzing—is more important than the product—the conclusions reached, the theories defended...
…we would never want to consign Descartes’ famous “cogito ergo sum” thought experiment, for example, to oblivion, even though none would accept its conclusions, it is just too nifty an intuition pump, even if all it pumps is falsehoods.
Dennett, Daniel C. (1995) Darwin's Dangerous Idea: Evolution and the Meanings of Life. Touchstone, New York.
