German philosopher Friedrich Nietzsche (and after him French philosopher Gilles Deleuze) used these categories to describe two different ways of acting and—by extension—being in the world. An action (which may be a thought, feeling, or practice) is active when it takes something as its object; conversely, it becomes reactive when it is made the object of someone or something else. Thus, if we feel sad (or happy) and we do not know why we feel this way, then we are reactive; if, however, we can discover the reason we are feeling this way, we can convert reactive forces into active forces. Reactive is not the same as negative and should not be thought of as intrinsically bad; it is, rather, the usual state of things. It is, however, a limiting state of things, because it separates us from what we can do—if we are sad for no apparent reason, and we do not seek out the cause, then we are prevented from forming an appropriate response to that cause, and our power to act is reduced. We are reacting when we could be acting, and more problematically still we are using our reaction to excuse our lack of action. Nietzsche generally refers to this state as ressentiment. Therefore, the challenge for both philosophy and life, according to Nietzsche, is to overcome the reactive state of things and become active, thereby constantly enhancing our power to act.

Further Reading:

G. Deleuze Nietzsche and Philosophy (1983).