simple

absolute arcadian austere bare barest benighted blockheaded careless chaste childlike classic clear clearest clean clean cleanest cleanest clearer commonest common credulous crudest crude daft daftest denser dense dimwitted doltish doting dopey downright down to earth dry dull duller dupable earthy easy as pie easiest easy easier effortless elegant facile familiar featherbrained feeble-minded fatuous foolish forthright gullible guileless harmless homelike homespun homey homely humblest humblest humble humble ignoble imbecilic imbecile ingenuous innocent literal loopy lowly low main mere mindless modest modest more elegant more familiar more readable more understandable more modest more modest more primary more primary more virginal more natural most primary most primary most virginal naive naked natural nominal nothing to it nothing to it oafish open and shut/open-and-shut open-and-shut ordinary oversimplified pastoral pellucid perfect plain plain primest primary/prime primary primitive pure purest readable rudimentary rude rural rustic rustic self-effacing senseless shallower shallow sheer silly simple-minded single slowest slower slow soft soft softer softer softheaded spartan spontaneous stark stupid thick-witted tomfool unaffected unassuming uncomplicated undiluted understandable unoffensive unintelligent unimposing unqualified unprocessed unmitigated unostentatious unpretentious unsuspecting unvarnished unwashed user-friendly unworldly virginal very voluminous