How Is It Silly to Ask If Higher Deficits Will Have a Negative Impact on Growth?

Clive Crook told readers in a Bloomberg column that:

"It’s silly to ask whether high public debt causes lower growth or vice versa as though it must be one or the other. Almost certainly, both are true. This reinforces the case for fiscal consolidation as the recovery strengthens -- not just to restore fiscal room for maneuver but also to support longer-term growth."

Both parts of this statement are close to ridiculous. How do we know that higher debt everywhere and always leads to slower gro...