Ataraxia, that tranquil state of lucid calm and health so highly valued by the Stoics and other ancient Greek thinkers, seems like one of those ideas that is difficult to articulate but universally obvious when in practice. The often misunderstood philosopher Epicurus seemed to believe that a very clear route to the nirvana-junior state of ataraxia is through a life lived with friends. To Epicurus, friendship is a stronger cornerstone to a healthy life than romantic love or wealth. Perhaps some of this noble feeling will be on display when the SB and Friends Tour visits The Outer Space tonight. Featuring hip hop artist Signor Benedick the Moor, Boston indie rapper Pink Navel, and L.A. indie rock and funk acts Kim Tillman and Orlando Kennedy, this 6:30 p.m. show should be a pretty bouncing good time ($7).