It is a history of the metaphilosophical discussions in Germany (mainly) from 1850 onwards. What should philosophy become now, was the question, now when no one has any confidence in systematic philosophy in the style of Hegel, and no one thinks that science is in need of a philosophical foundation. The discussion at the time concerned how to make philosophy scientific. And the form of the question was: which science should philosphy submit itself to in order to be useful? Which science should give philosophy its task and material. That question gave rise to a number of kinds of philosophies, caliming ti be the Philosophy: philosophy of mind and phsychologism, in relation to psychology; philosophy of language, naturalism, in relation to physics, biolgism; but also philosphy of history, in a new sense, and history of philosophy as philosophy itself (also that in a non-hegelien sense).
It is a little known period in German philosophy. The auther wants to show that for exemple Karl Löwiths book, From Hegel to Nietzsche, gives an unhistorical history of the phiolsophy of that period, since neither Marx, Feuerbach or Kierkegaard had any influence what so ever. On the contrary, Schopenhauer had many followers during that period, and was regarded as a possible starting point for a scientific philosophy.