Seeing is believing?

It has been said "unless I can see it I won't believe it", so "seeing is the only absolute basis for belief". Well, I'm not sure I follow this logic. Take wind, although we can't see it - we can observe what it does, we can feel it, we can experience it, we can measure its effect and impact. So, the fact we can't actually see wind, doesn't mean it doesn't exist.
It is the same for generosity and grace. They can't be seen but we can experience the life changing outcomes that come as a direct result of an outbreak of generority and grace. Grace and generosity can, and indeed do, demolish intractable problems. They operate almost as a conspiracy, being unleashed through groups of inconspicuous people, taking decisions to share these gifts with others. Long may the conspiracy thrive.