Alan Dershowitz is downsizing. The celebrated Harvard Law professor who’s been selling off his art collection in recent months has now put his Cambridge home on the market. The asking price? A paltry $3.95 million. Reached Tuesday, Dershowitz told us it was difficult to consider selling, but his three children are all out of the house and he and his wife, Carolyn Cohen, intend to spend more time in New York and Florida in the coming years. (Dersh will be done teaching at Harvard after next year.) The house, located on Reservoir Street, has three bedrooms, an indoor lap pool, a hot tub, a gym, and a Japanese garden. Then there are all the stories the walls can tell. “A lot of interesting people have had dinner there,” said Dershowitz. “Benjamin Netanyahu , Elie Wiesel , Eliot Spitzer , Bill Weld , Claus von Bülow , Leona Helmsley . . . . A lot of ghosts have walked those halls.” He bought the 5,451-square-foot home in 1990 for $1.15 million.