Paragraphs are the units of scholarly prose composition. They normally consists of at least six sentences and at most 200 words that support, elaborate or defend a single well-defined claim. The claim is stated in the “key sentence”, and the rhetorical posture of the paragraph depends on the difficulty that this sentence presumably poses for the reader. If the reader should find the claim hard to believe, the paragraph will support it with evidence. If the reader should find the claim hard to understand, the paragraph will elaborate on it with description or definition. (This paragraph, for example, elaborates on the composition of paragraphs.) If the reader, having already formed a contrary opinion, finds it difficult to agree with the claim, the paragraph will defend the claim against the reader’s objections. Whatever its posture, the sentences in the paragraph are trying to leave the claim in the key sentence with the reader. It is what readers should take with them into the next paragraph. A simple list of the key sentences in a scholarly text, therefore, should provide an accurate sketch of the whole composition.