The document discusses four principles of language:
1. Directness - Language should be active, personal, and use "you" to directly address the audience.
2. Abstraction - Language should be specific rather than abstract.
3. Objectivity - Words can have both denotative and connotative meanings, so speakers should consider how audiences may interpret terms.
4. Formality - Language should be at a slightly formal level, using common words and informal constructions that are not incorrect. The summary captures the key points about the four principles of language discussed in the document.