This text explores the ontological relationship between activity and change. The author challenges the Aristotelian tradition by asserting that activity is inherently a form of change, as static entities are incapable of action. Activity is not only a change in itself but also a catalyst for further changes in other entities. The fundamental distinction between simple change and activity lies in the presence of a subject. While change can be analyzed objectively without reference to an agent, activity is always the activity of a subject. Describing activity solely from an external perspective, while ignoring or denying the subject, results in a reductionist view that strips reality of a vital dimension. A subject must not be reduced to an object or defined merely by external contexts. Instead, the subject is the prerequisite for establishing active connections. Through their activity, subjects initiate relationships and shape reality, a process that cannot be fully captured by external observation alone.