What is Philosophy? (According to Some Philosophers)

"Philosophy aims at understanding what is unchangeable, eternal, in and for itself: its end is Truth. But history tells us of that which has at one time existed, at another time has vanished, having been expelled by something else. Truth is eternal; it does not fall within the sphere of the transient, and has no history. But if it has a history, and as this history is only the representation of a succession of past forms of knowledge, the truth is not to be found in it, for the truth cannot be what has passed away."

— Georg Wilhelm Friedrich Hegel, Lectures on the History of Philosophy

"For the investigator of experience it is really only a matter, here just as there, of his having the rational discipline belonging to his sphere and, where he has it imperfectly, of acquiring it through the actual effecting of the eidetic attitude and the investigations that are to be freely shaped within its framework. Thereby it is purely a question of his doings and not of his reflective "philosophical" ideas about it: as, indeed, it does no harm at all when the scientific investigators of nature, after they have done geometry in the eidetic attitude, not at all rarely explain afterward that this is nothing other than empirical science. Quite otherwise when the prevailing interests are precisely not experiential-scientific ones, but rather ones belonging to the theory of science, metaphysical ones, philosophical ones in some good sense, and when in particular the psychologist himself claims to be a philosopher at the same time. If he is not able to get rid of his prejudices that so easily become involved with the naive and experiential-scientific attitude, then he simply cannot be a genuine philosopher; he then engages in a shallow philosophy, a monster of natural science and philosophy. If he does not want that, then he must gain pure clarity, as we others do from the outset claim to be philosophers and nothing else."

— Edmund Husserl, Ideas Pertaining to a Pure Phenomenology and to a Phenomenological Philosophy, Third Book: Phenomenology and the Foundations of the Sciences

"[P]hilosophy is not a simple art of forming, inventing, or fabricating concepts, because concepts are not necessarily forms, discoveries, or products. More rigorously, philosophy is the discipline that involves creating concepts.

[...] We can at least see what philosophy is not: it is not contemplation, reflection, or communication. This is the case even though it may sometimes believe it is one or other of these, as a result of the capacity of every discipline to produce its own illusions and to hide behind its own peculiar smokescreen.

[...] To know oneself, to learn to think, to act as if nothing were self-evident—wondering, "wondering that there is being"—these, and many other determinations of philosophy create interesting attitudes, however tiresome they may be in the long run, but even from a pedagogical point of view they do not constitute a well-defined occupation or precise activity. On the other hand, the following definition of philosophy can be taken as being decisive: knowledge through pure concepts. But there is no reason to oppose knowledge through concepts and the construction of concepts within possible experience on the one hand and through intuition on the other. For, according to the Nietzschean verdict, you will know nothing through concepts unless you have first created them—that is, constructed them in an intuition specific to them: a field, a plane, and a ground that must not be confused with them but that shelters their seeds and the personae who cultivate them."

— Gilles Deleuze and Felix Guattari, What is Philosophy?

"2. World outlooks are represented in the domain of theory (science + the 'theoretical' ideologies which surround science and scientists) by philosophy. Philosophy represents the class struggle in theory. That is why philosophy is a struggle (Kampf said Kant), and basically a political struggle: a class struggle. Everyone is not a philosopher spontaneously, but everyone may become one.

"3. Philosophy exists as soon as the theoretical domain exists: as soon as a science (in the strict sense) exists. Without sciences, no philosophy, only world outlooks. The stake in the battle and the battle-field must be distinguished. The ultimate stake of philosophical struggle is the struggle for hegemony between the two great tendencies in world outlook (materialist and idealist). The main battlefield in this struggle is scientific knowledge: for or against it. The number-one philosophical battle therefore takes place on the frontier between the scientific and the ideological. There the idealist philosophies which exploit the sciences struggle against the materialist philosophies which serve the sciences. The philosophical struggle is a sector of the class struggle between world outlooks."

— Louis Althusser, "Philosophy as a Revolutionary Weapon"

"[I]f everything is dead already, this is not only because extinction disables those possibilities which were taken to be constitutive of life and existence, but also because the will to know is driven by the traumatic reality of extinction, and strives to become equal to the trauma of the in-itself whose trace it bears. In becoming equal to it, philosophy achieves a binding of extinction, through which the will to know is finally rendered commensurate with the in-itself. This binding coincides with the objectification of thinking understood as the adequation without correspondence between the objective reality of extinction and the subjective knowledge of the trauma to which it gives rise. It is this adequation that constitutes the truth of extinction. But to acknowledge this truth, the subject of philosophy must also recognize that he or she is already dead, and that philosophy is neither the medium of affirmation nor a source of justification, but rather the organon of extinction."

— Ray Brassier, Nihil Unbound: Enlightenment and Extinction