Philosophy can only be approached with the most concrete comprehension.

Only then, approaching my fortieth birthday, I made philosophy my life's work.

If philosophy is practice, a demand to know the manner in which its history is to be studied is entailed: a theoretical attitude toward it becomes real only in the living appropriation of its contents from the texts.

Philosophy is tested and characterised by the way in which it appropriates its history.

Only as an individual can man become a philosopher.

As a universal history of philosophy, the history of philosophy must become one great unity.