Final answer:
The intention behind Flecknoe's statement is to encourage creativity.
Step-by-step explanation:
The intention behind Flecknoe's statement that any sharp thoughts his son Shadwell has in his mind will die when they touch his pen is to encourage creativity. Flecknoe hopes that his son's writing will be devoid of originality and inspiration, effectively stifling any innovative or insightful ideas. By sarcastically stating that Shadwell's thoughts will perish when he tries to write them down, Flecknoe is critiquing his son's lack of creativity and talent as a writer.