Causation and reasoning are different but related types of relationships. Both causal relations and reasoning processes may be expressed with one and the same connective word in some languages: English speakers use because and Japanese speakers use kara. How then are causation and reasoning processes related to and different from each other? How do we construe and encode them? How is because different from other conjunctions with similar meanings?To account for these and related empirical questions, this book presents an integrated analysis in accordance with the original principles of Construction Grammar. In particular, the book shows that the analysis proposed is compatible with our general knowledge about causation and reasoning and that it is valid for English and Japanese. The proposed analysis is also comprehensively applicable to a variety of related phenomena, ranging from the just because X doesn't mean Y construction to the innovative and less known because X construction.