Here's why:
* Shakespearean Influence: The phrase draws heavily on Shakespeare's play "Macbeth" where Macbeth says, "Life's but a walking shadow, a poor player / That struts and frets his hour upon the stage, / And then is heard no more." While not an exact match, the phrase reflects a similar sentiment about the transient nature of life.
* Biblical Echoes: The idea of life being "a fleeting shadow" also echoes the book of Psalms in the Bible, where it states, "Our days on earth are like a shadow, a breath that soon fades away."
* Popular Usage: Over time, the phrase has been adapted and used in numerous works of literature, poetry, and even music.
Therefore, the phrase "Life is but a fleeting shadow" is not attributed to a single author but rather reflects a common theme explored in different forms throughout history.