This term refers to one of the twenty-four styles of poetry as propounded by SikongTu(837-908 ) of the Tang Dynasty and falls into a very important classic aesthetic category, An unrestrained and ingenuous spirit reflects a state of “carelessness” in poetic creation, whereby the poet allows his inner self to encounter external things without constraint, It does not choose any particular scenery and subject matter. It neither shows favor to any particular technique or means of expression, nor does it pay undue attention to wording. As a poetic style and a creative mindset, an unrestrained and ingenuous spirit does not mean arbitrariness, petulance or lack of method, Instead, it aims to shake off the influence of any preconceived idea or subconscious thought, yet respect prior cognitive and aesthetic experience. It represents not only a natural, quietly elegant, and unrestrained aesthetic style, but also a magnanimous mind and an elevated state of being.

When a poet demonstrates a free and ingenuous spirit, he writes in a relaxed style. Shi Jiaoran: Poetic Styles 

Poetry embodies true feelings and gives free rein to the poet's true self. Provided that his soul remains in control of all things and the images created by him are natural and wide-ranging, the poet can be expected to write in a natural, flowing style. He may build a hut under a pine tree, remove his hat, and read at ease. All that catches his attention is sunrise alternating with sunset. He hardly bothers about which time he is in. He pursues a carefree way of life without any higher goal. So long as he follows the natural course, he will experience the delights of a free, uninhibited life. Sikong Tu: Twenty-four Styles of Poetry