 A central notion in argument-based formalism is argumentative attack. We can, for instance, distinguish between rebuts and undercuts. A rebut of an argument \((\Theta, \tau)\) is an argument that establishes that \(\tau\) is not the case, viz. an argument for \(\neg\tau\). An undercut of \((\Theta, \tau)\) establishes that \(\Theta\) does not support \(\tau\). For instance, the argument that concludes that an object is red from the fact that it looks red, is undercut by means of the observation that that object is illuminated by red light  (Pollock 1995).  Note that in order to undercut an argument for \(\tau\) one need not establish that \(\tau\) doesn’t hold. 