 This idea does, however, raise a number of difficult issues. One such issue concerns the relationship of autonoetic consciousness to other forms of consciousness. Tulving contrasts autonoetic (self-knowing) consciousness with noetic (knowing) and anoetic (nonknowing) consciousness, where noetic consciousness refers to the consciousness of remembering that accompanies semantic memory and anoetic consciousness refers to a basic awareness of ongoing experience. The relationships among these forms of consciousness are complex (Vandekerckhove &amp; Panksepp 2009) and have yet to be explored in detail by philosophers. Their relationships to the form of temporal consciousness at issue in awareness of the ongoing flow of time (Arstila &amp; Lloyd 2014; McCormack 2015) likewise have yet to be explored. Another issue concerns the role of autonoesis in forms of mental time travel other than episodic memory. Episodic memory is increasingly understood as a form of past-oriented mental time travel on a par with future-oriented mental time travel, or episodic future thought (Suddendorf &amp; Corballis 2007). While the standard view is that autonoesis is a necessary feature of both episodic memory and episodic future thought, some researchers have questioned the necessity of autonoesis for episodic future thought (De Brigard &amp; Gessell 2016; Klein 2016a; Klein &amp; Steindam 2016; Perrin 2016).