Look at how they play off each other excitedly. The tree bends toward the saint. The rock face curves behind to embrace him. Vines twist to outline his cell. The velvety sunlight sharply etches the anatomy of his cheeks.
Nothing here is clearly natural, supernatural, or artificial.
A viewer's eyes can follow as one line of indentation in stone is adapted to a man-made seat. This is neither the city depicted at top left, nor a self-contained landscape like the sheer rock at the upper right, but an altogether different world. Here it is unclear where nature or civilization leaves off. Just as the sun and the tree bow to meet Saint Francis, he has turned to meet them. He leaves behind him the cave, with its darkness and dry skull recalling death.