"I fear the man of one book" - What is your attitude towards this thought?

A while ago I heard said phrase being interpreted as a warning toward people who only have knowledge from a single source (a single book, the oneself's perspective, a single author, a single teacher, etc.). Buddhism touches a lot of topic today divided into individual sciences and knowledges of their own. That's why the Dhamma is usually classified as a philosophy, a psychology, a religion, and so on. But in Buddha's time and considering the purpose of the Dhamma, those bounderies where useless and alien to the practice itself. The Buddha used elements from all sorts of areas and knowledges in order to eradicate Dukkha and to reach the other shore. In modern times, we know a lot more about the working of the brain, about human physiology, about philosophy and science in general, about the development of religions and cultures, and about the world in general. With that in mind: should we fear the men of one book? Should the ones following the Dhamma know and study these other areas in order to contrast and prove the reality of the Buddha's words? Or is it enough with just reading Dhamma books? If you lean on that second field, do you trust that the Buddha was inerrant and/or that the authors of the Suttas had the Buddha's words transcribed verbatim? I'm not sure if this kind of questions are appropiated for this site. If not, just ignore it and close it. EDIT: What motivated this question is that strange vibe that arises when I read discussion where people base their answers and arguments only on suttas and Dhamma books. While that's OK, specially on academic sites, it's pretty weird to me that such an experiential and pragmatic thing as the Dhamma is, is a lot of times covered by a dogmatic and scholar aura, which puts in motion endless debates about the nature of consciousness, the place where kammic seeds are stored, the time it passes before rebirth and that sort of things. But I always end with this question in my head: are people telling about X thing because they have experienced themselves such phenomena, or because the suttas said so, or both? EDIT 2: Wow! Such good answers! I cannot pick one over another. For these cases, I'd love to choose more than one. Thanks for those well thought and well put idea! Thanks for your time and patience!