Why are the “categories "true and false" so inadequate” in the case of philosophy?

Directions: Answer the question based on the following passage.

Metaphysical principles are less easily verified from experience than physical hypotheses, but also less easily refuted. Systems of philosophy, therefore, are not so dependent on our progressive knowledge of facts as the theories of natural science, and change less quickly; notwithstanding their mutual conflicts, and in spite of the talk about discarded standpoints, they possess in a measure the permanence of classical works of art, they retain for all time a certain relative validity. The thought of Plato, of Aristotle, and of the heroes of modern philosophy is ever proving anew its fructifying power. Nowhere do we find such instructive errors as in the sphere of philosophy; nowhere is the new so essentially a completion and development of the old, even though it deem itself the whole and assume a hostile attitude toward its predecessors; nowhere is the inquiry so much more important than the final result; nowhere the categories "true and false" so inadequate. The spirit of the time and the spirit of the people, the individuality of the thinker, disposition, will, fancy--all these exert a far stronger influence on the development of philosophy, both by way of promotion and by way of hindrance, than in any other department of thought. If a system gives classical expression to the thought of an epoch,’ a nation, or a great personality; if it seeks to attack the world-riddle from a new direction, or brings us nearer its solution by important original conceptions, by a subtler or a simpler comprehension of the problem, by a wider outlook or a deeper insight; it has accomplished more than it could have done by bringing forward a number of indisputably correct principles.