Psychoactive substances and their properties have been known to us since the dawn of civilization.
'Hallucination' comes from the Latin "alucinari" meaning "to wander in the mind". The origin of a word elucidates its true meaning.
Hallucinogen denotes psychoactive material which is the cause of prominent changes in perception, thought and mood.
Psychedelics are 5-HT2A partial agonists [serotonergic hallucinogens] and are generally either Phenethylamine, Tryptamine or Lysergamide, e.g. Mescaline, Psilocybin and Lysergic Acid Diethylamide. Dissociatives are NMDA antagonists, usually Arylcyclohexylamine compounds which cause anesthesia, e.g. Ketamine and Phencyclidine. Deliriants are anticholinergics that consistently cause acute confusion and are often extremely poisonous e.g. Atropine and Scopolamine.
We live in a diverse universe, Far larger than you or I; Exploring it expands our minds.