Activism, in a general sense, can be described as involvement in action to bring about change, be it social, political, environmental, or other change. This action is in support of or opposition to one side of a controversial argument.
There are many different forms of activism; a select list follows.
... (1836)
Psychologie oder Wissenschaft vom subjektiven Geist (1837; 3rd ed., 1863)
Kritische Erläuterungen des Hegelschen Systems (1840)
Vorlesungen über ...