In recent blog discussions, I have encountered familiar arguments against philosophy: it's not a science, it's endlessly up for debate, it's merely a matter of opinion. I would respond to this line of thinking with what might be a novel rebuttal for many readers. This post is motivated by the continuing discussion at Three Pound Brain.
Philosophy is transformative of its practioners, and I propose that to be its primary purpose. Philosophy, as the love of wisdom, is not aimed at knowing theory, and thus criticisms based on the gap between the stability of philosophical versus scientific conclusions aim at the wrong target and are fallaciously beside the point. Philosophic practice renders a person capable of the finest critical, rational thought and that is its primary purpose, not theory-craft.
Whenever philosophy achieves heights of success, that field becomes a science, which is another reason why criticism of philosophy is misguided. Its own success has become a mark against it, since only the science of logic has remained its own. Every time science is lauded over philosophy, one blinds oneself to science's origins, and may I suggest, is in danger of reducing science to technology and current practices (techne) while momentarily forgetting the theoretical framework that founds those practices (theoria). I'm alluding to Kuhnian and Heideggerian counter-critiques.
Academic philosophy, in its current disciplinary and institutional situation, is likely the real target of such criticisms. Yes, few academic philosophers who want to hold a job would publicly admit that publish or perish, Sisyphean workloads, and a number of other factors have bloated academic discourse and publications for fear that they would implicate themselves. However, that is again a contingent and side-issue.
Philosophy handles fields that empirical science cannot in at least three ways. First, normative studies cannot be a science. I suspect this is often over-looked, because many engaging in anti-philosophical conversations do not hesitate to conflate normative and descriptive theories; e.g., there is nothing more to morality than what people happen to accept. Second, as a theoretical discipline, science is not self-sustaining. For example, we will always need a theory of evidence before we have evidence, because nothing in the world ever speaks for itself. Meaning is always in part a human construct, and we cannot perform scientific practice without making the world meaningful, which cannot be self-contained within empirical science. This is a well-tread area of scholarship in the philosophy of science. Third, not every field of study can be a science or is yet an empirical science. For instance, the value fields, e.g., politics, ethics, aesthetics, etc. cannot be a science, because their object is not a natural thing or kind, which does not imply that the results of such fields are a mere matter of opinion. If you think so, I suppose the difference between a liberal democracy and a cannabalistic tyranny is merely a matter of opinion, as opposed to the former being a more stable form of government. Seriously, many very useful ideas cannot be reduced to some material, energetic, or law-like correlate, and that does not render those ideas pure fantasy.
I will propose one well-known way to adjudicate between philosophic theories. What difference does the theory make? An ethic can never be reduced to science, but the scientific study of the consequences of its adoption can be the subject of scientific study. Would we then claim that ethic for science and not philosophy? I hope that the reader realizes at that point the distinction becomes foolish.
In sum, blaming philosophy for not being a science misconceives both what philosophy and science are or can be. There may be philosophies that do not fit the mold described here, but that is another matter, and they can fend for themselves.