A Ghost of a Chance (1973)

Jerry just can't seem to shake off the death of his lover Cass, who he keeps seeing wherever he goes. But Cass is real and explains why he's back and can't be seen by others. They go to a bar where Cass, naked and invisible to everyone except Jerry, describes all of the things he's learned in death while offering his theories on why men should have sex with whomever they want, even if they're in a monogamous relationship.