First things first: There is a difference between absinthe and pastis. Absinthe and pastis are both generic names for different licorice-flavored liquors. That, pretty much, is where the similarities end. Pastis is a generic name for a liqueur flavored with star anise, whereas absinthe is a spirit made from various herbs, sometimes including European green wormwood, which gives it its licorice-like flavor. Pastis liqueurs are a sweet after-dinner drink (think Sambuca), as opposed to a spirit, which has much less sugar – gin, whiskey, etc.
Absinthe has a much more storied past, with tales of hallucinogenic qualities, a cause of decadent behavior and general insanity – let’s not forget Van Gogh losing an ear – however, these are mostly myths. The various tales of absinthe-induced insanity and absinthe as a quick route to tripping actually started a type of prohibition in parts of southern Europe, where it was most popular.
These myths were popularized by the young bohemians of the day, who drank it after its controversial change in legal status around 1915. History has recently repeated itself with the introduction of the now-legal absinthe in the United States and Europe, where rumors of absinthe’s unique powers are used by marketers to hype a “new" product. Friends, it is all bullshit.
Yes, you can die of wormwood overdose (the active ingredient being thujone), but it would not be from consuming absinthe. To reach a toxic dose, the alcohol would do the job before the wormwood. Does absinthe taste good? Well, to each his own, but it’s not my thing. I appreciate the history and ritual of the absinthe fountain, the spoon, the water and sugar, but its appreciation tends to end at my lips.
Pastis has been popular in its many forms, such as Sambuca, Anisette and Pernod. It was originally produced as a legal substitute for absinthe. Sweet and rich in flavor, this star anise–fennel flavored liqueur is favored as an after-dinner drink throughout Italy, southern France and Spain, as well as here in the States. Its strong flavor, when used judiciously, is used in both cooking and in cocktails. It is used by many chefs as a complement to seafood, and I have personally used Pernod to make gravlax a few times. Bartenders use it to make a traditional Sazerac, a combination of rye whiskey, lemon and either Pernod or an absinthe named Herbsaint.
The base for both absinthe and pastis is a clear alcohol that is redistilled with the various herbs and roots that give them their unique flavor profiles. This is not unlike making gin, as all gin is a neutral spirit (basically vodka) until the maceration and re-distillation of the final ingredients takes place.
I suggest you drink absinthe or pastis with some discretion, as they will both punish you a bit, especially the next day. Then again, one man’s temperance is another man’s debauchery. As Ernest Hemingway put it in his famed recipe for the cocktail appropriately called Death in the Afternoon: "Pour one jigger of absinthe into a Champagne glass. Add iced Champagne until it attains the proper opalescent milkiness. Drink three to five of these slowly.” (Hence the name.) Cheers!