Volume two contains books III and IV of An Essay concerning Human Understanding. In book III, Locke presents his theory of language. He connects words with the ideas they signify. He then critiques the abuse of words by philosophers who make up new words not connected to a clear idea or connect old words to new ideas.
In book IV, Locke lays out his general theory of knowledge. He defines knowledge as the sum of one’s ideas and perceptions. He looks at the limits of knowledge and the divide between purported knowledge and reality—the divide, in other words, between a person’s claim of knowledge (based on their experience) and reality, which might not correspond to that knowledge.
This volume is linked with the other texts in your Logos library, allowing you to cross-reference important words with a click. This is particularly helpful, as philosophers were in constant dialogue with each other’s works—critiquing, supporting. Now you can see the cited works in context in seconds. Moreover, every word is indexed for remarkably fast searching. Search results show up with a helpful context snippet, so you can quickly get the reference you’re looking for.