Much of the rhetoric spread by jihadist organisations seems to indicate a strong commitment towards a set of religious and political ideas. But does cognitive extremism really lead to violent extremism? Terrorism scholars have been divided by this question for over a decade now. This article summarises and reflects upon the key theoretical debates about the question whether cognitive extremism really is a precursor for violent extremism. Using Schmid’s distinction between non-violent and not-violent political movements, it argues that even though there is no linear path from adopting extremist ideas towards committing acts of violence, cognitive extremism of some extent seems to be a necessary precondition for violent extremism and that beliefs always play a, though not necessarily the central role. This however does not mean that cognitive extremism is a great predictor for eventual violent extremism or that violent extremists are necessarily the most ideologically radicalised.