David Hume, a Scottish philosopher in the 18th century, is famous for skepticism on the objectivity of causality and validity of moral judgment. But his assertion that causes and effects, "is" and "ought" are distinct and the connections between them are uncertain because of their subjectivity puts the cart before the horse. The fact is that, as the subject encounter uncertain affairs, it must divide them into causes and effects or "is" and "ought" so as to reduce uncertainty.

What is the difference between reason and cause? Have you thought these are similar terms to explain something? Philosophically these two should be distinguished.