 Finally, we have the Argument from Computational Tractability (Carruthers, 2006, pp. 44–59). For the purposes of this argument, we assume that a mental process is computationally tractable if it can be specified at the algorithmic level in such a way that the execution of the process is feasible given time, energy, and other resource constraints on human cognition (Samuels, 2005). We also assume that a system is encapsulated if in the course of its operations the system lacks access to at least some information exogenous to it.