You need to memorise enough of the topic to know what to look up in a book. You need to memorise enough of the topic that you can draw relationships between di

You need to memorise enough of the topic to know what to look up in a book. You need to memorise enough of the topic that you can draw relationships between disparate elements. Having content in your memory means you have the ability to potentially pull it up quicker, or to pull it up in a situation (such as a team meeting) where you don't have access to the book. If you rely only on what's previously written, foregoing memorisation, you are limited to the relationships that other people have written down.