Humans' capacity to attain knowledge is central to Spinoza's philosophy because, in part, knowing things enables humans to deal properly with their affects. But it is not just any sort of knowledge that humans should attain. There are different types of knowledge, but only two of them–rational and intuitive knowledge–enable humans who attain them to know things clearly. Because rational knowledge attends to universals whereas intuitive knowledge attends to particulars, intuitive knowledge is better than rational knowledge at enabling humans to (...) deal with their affects. Most scholars recognize both the importance of knowledge to humans' dealing with their affects and the superiority of intuitive knowledge at enabling them to do this. But these points are particularly relevant to the affect that Spinoza calls "tristitia," which is usually translated as either "pain" or "sadness." I argue in this dissertation that attaining knowledge– especially intuitive knowledge–enables humans to deal properly with their experiences of pain. This ability that humans acquire by knowing things is what I call "active suffering." A person suffers passively when she merely reacts to her pain, in this way allowing an external force to control her. She suffers actively when she uses knowledge to respond to her pain, in this way being in control of herself. This knowledge she uses to deal actively with her pain bears a relation to Spinoza's theory of freedom, since it entails a realization that all events (such as a person's experience of pain) happen necessarily and that embracing this necessity is the same as being free. (shrink)