Ingesting a powerful dose of a psychedelic drug is like strapping oneself to a rocket without a guidance system. One might wind up somewhere worth going, and, depending on the compound and one’s “set and setting,” certain trajectories are more likely than others. But however methodically one prepares for the voyage, one can still be hurled into states of mind so painful and confusing as to be indistinguishable from psychosis. Hence the terms psychotomimetic and psychotogenicI are occasionally applied to these drugs.