The phrase "pure imagination" refers to the ability to create and visualize things in one's mind without any limitations or restrictions. It is a creative process that allows individuals to envision ideas, concepts, and possibilities that may not exist in reality but can be brought to life through imagination. In other words, it means using your thoughts and mental powers to dream up new ideas, create artistic masterpieces, or imagine different scenarios without being bound by the constraints of what is currently known or experienced.