Our claim, then, can be put simply: Philosophy should never have been purified. Rather than being seen as a problem, “dirty hands” should have been understood as the native condition of philosophic thought — present everywhere, often interstitial, essentially interdisciplinary and transdisciplinary in nature. Philosophy is a mangle. The philosopher’s hands were never clean and were never meant to be.

There is another layer to this story. The act of purification accompanying the creation of the modern research university was not just about differentiating realms of knowledge. It was also about divorcing knowledge from virtue. Though it seems foreign to us now, before purification the philosopher (and natural philosopher) was assumed to be morally superior to other sorts of people.

The 18th-century thinker Joseph Priestley wrote “a Philosopher ought to be something greater and better than another man.” Philosophy, understood as the love of wisdom, was seen as a vocation, like the priesthood. It required significant moral virtues (foremost among these were integrity and selflessness), and the pursuit of wisdom in turn further inculcated those virtues.

The study of philosophy elevated those who pursued it. Knowing and being good were intimately linked. It was widely understood that the point of philosophy was to become good rather than simply to collect or produce knowledge.

As the historian Steven Shapin has noted, the rise of disciplines in the 19th century changed all this. The implicit democracy of the disciplines ushered in an age of “the moral equivalence of the scientist” to everyone else. The scientist’s privileged role was to provide the morally neutral knowledge needed to achieve our goals, whether good or evil. This put an end to any notion that there was something uplifting about knowledge. The purification made it no longer sensible to speak of nature, including human nature, in terms of purposes and functions.