Meet the modern Playmate. She paints. She reads philosophy. She ponders the meaning of life, the meaning of sex, even the sociopolitics of appearing in Playboy - as the historic 500th Playmate. Of course Alicia Rickter also looks super in a bikini - or better still, dressed in that important Sartrean concept: nothing. She's no ordinary 23-year-old; then again, the ordinary doesn't really register on the Rickter Scale of Being. What matters to Alicia is testing life's limits -- shaking up the world a little, taking chances. These days that means transforming from jet-setting model to night-school student at Cal State, where tonight she's late for psych class. She flew home earlier in the day from a swimsuit-modeling gig in Cancún, then sped straight to school. That beep in her purse as she tries not to be noticed? Just her modeling agency paging its prize offering. Relaxing on the floor in her bedroom, Alicia listens to a Sting CD. Around her is a gallery of Rickterabilia: a century-old antique bed, texts on art and psychology, the dolls of a little girl, the cellular phone of a businesswoman. Sting sings a bit, then Alicia talks about being stung.