Why did Pliny the Elder choose the title Natural History?

Pliny the Elder chose the title Natural History (Naturalis historia) to reflect his purpose of studying "the nature of things, that is, life".1

In the preface to his 37-volume work, dedicated to the emperor Titus, Pliny justified the title on utilitarian grounds. He sought to compile and organize older, scattered material that belonged to "encyclic culture" (enkyklios paideia), a task he noted had not been previously attempted. By creating this encyclopaedic work, he aimed to provide a comprehensive record of the natural world, covering subjects ranging from astronomy and geography to zoology, botany, medicine, and geology.12