Why did Dong Qichang like to learn Su Shi's calligraphy in his later years?

In his later years, Dong Qichang liked to learn Su Shi's calligraphy, which was naturally influenced by Dongpo's literary theory of "getting old and familiar, but returning to simplicity". At this time, his calligraphy, especially cursive script, is not only square and dignified in style, but also sharp in brushwork and thick in ink color, which are rare. However, it is more dry pen and light ink, with thin lines and very light and far-reaching artistic conception. It is no longer appropriate to use the word "Cang Xiu" to describe it. The representative works of this period include Zhang Jiuling's Fu Juan with White Feather Fan, Dong Fangshuo's Difficult Volume to Answer Guests, Zhao Meng's Four Postscripts of Quehua Autumn Volume, Yan Zhenqing's Book for Seats, Cursive Poems and Five-character Poems.

At the same time, the formation of Dong Qichang's calligraphy style is also closely related to his efforts in using pen, writing, composition and ink. Dong Qichang has been tirelessly exploring traditional brushwork all his life. After studying a large number of ancient calligraphy posts, his deepest experience is the "emptiness" of the pen. He believes that only the pen is empty and harmonious, and the charm is born under the wrist; Only by "not making a real pen" can there be an ever-changing "no sag, no shrinkage, no harvest". In addition, in the knot, Dong Shi pays attention to implication, compactness and strength; In composition, inspired by Yang Ningshi's Jiuhua Tie and Immortal Living Method, he attaches great importance to the principle of alternating density and density, and increases the distance between words and lines to strengthen the visual contrast between black and white and reality, thus creating a simple and far-reaching artistic conception; In using ink, he attaches great importance to "using ink must make it moist, not boring, especially avoiding agricultural fertilizer, which is a great evil."