This quote by Thomas Aquinas is a cautioning to be cautious of individuals who only have understanding from one source. It indicates that those who only depend on one book for their understanding are restricted in their understanding of the world. They may be not able to think seriously or objectively, and might be more likely to be swayed by their own biases and presumptions. This can result in a narrow-mindedness that can be dangerous in particular scenarios. It is important to be open up to various point of views and to seek out understanding from a variety of sources in order to get a more extensive understanding of the world. By doing so, we can end up being more informed and much better equipped to make decisions and form opinions.
