Australia’s counterterrorism policy is often justified publicly by the perceived threat of radicalisation. The purported rise of radicalisation, however, is based on conflicting academic opinion and limited empirical evidence. This article examines the radicalisation discourse and argues that there is no consensus in the field as to how a person can become radicalised, or even what the end point of radicalisation should be. Furthermore, scholars are yet to formulate a persuasive explanation for how ideas can actually lead to violence. The radicalisation debate may result in the securitisation of unconventional views, which could threaten the freedom of political discourse that underpins the Australian democratic system.