"Philosophers are not honest enough in their work, although they make a lot of virtuous noise when the problem of truthfulness is touched even remotely. They all pose as if they had discovered and reached their real opinions through the self-development of a cold, pure, divinely unconcerned dialectic...; while at bottom it is an assumption, a hunch, indeed a kind of "inspiration" most often a desire of the heart that has been filtered and made abstract that they defend with reasons they have sought after the fact."

Source: Beyond Good and Evil. Book by Friedrich Nietzsche, Part One: On the Prejudices of Philosophers, §5., 1886.