First, I'll check if "The Voice of the Mind" by Edgar F. Herbert is a known work. A quick mental search (since I can't actually browse the internet) tells me that Edgar F. Herbert isn't a familiar name in literature or philosophy. There's also a possibility that the user might be referring to a lesser-known or perhaps a fictional work. The term "Caesari" could be part of the title or another book. However, since the user mentioned a PDF version, maybe this is an online text? Sometimes PDFs can be self-published works or academic papers that aren't widely known.