inasmuch as

The formal conjunction inasmuch as implies a reason for an occurrence or action while suggesting concession; the main statement is true in view of the circumstances introduced by this construction: Inasmuch as I was tired, it seemed best to sleep. Because introduces a direct reason: I was sleeping because I was tired. The reason, proof, or justification introduced by for is like an afterthought or a parenthetical statement: I was famished, for I had not eaten all day. As and since are so casual as to imply merely circumstances attendant on the main statement: As (or since) I was tired, I was sleeping.