"The mood in which my book was conceived and executed, was in fact to some extent a passing one"

In this quote, F. H. Bradley is describing the mood in which he wrote his book. He is suggesting that the mood he was in while writing the book was not a long-term one, however rather a passing one. This could suggest that the emotions he was feeling while writing the book were short lived and not always reflective of his overall frame of mind. It could likewise suggest that the concepts and styles he was checking out in the book were only pertinent to the time period in which he composed it, and not always relevant to other times. Bradley is suggesting that the mood he remained in while composing the book was not a long-term one, which the concepts and styles he checked out in the book were just pertinent to the time duration in which he composed it.