Thanks for doing this, Pen. The topic seems to me clearly an important but difficult one. But it seems to me fine if depth overlaps other properties such as fruitfulness, interconnectedness, unifying in surprising ways, etc. It also seems fine (compatible with an objectivist view that at least a great deal of non-constructivist mathematics is definite in classical truth-value) if depth both has objective significance and is interest-dependent. I look forward to seeing the volume.