There's a difference between subjectively sensing the "duck" and a duck actually existing. There is a palpable difference between the reality we sense and the reality that actually exists, as has been proven many times by science.

You have to be careful equating our experience of reality with reality itself, because everyone's reality is different... sometimes with gross incompatibilities. Just because you've "seen" or "heard" something, doesn't mean you actually saw or heard it. It means your brain registered it, and there's a pretty big disconnect between that and objective reality. Even worse, it boggles most conceptions of the universe that multiple, valid "realities" are hanging around; either there's an objective reality we perceive imperfectly, or we live in a completely chaotic universe where the only reason we think it makes sense is we "remember it making sense"... as if memory makes sense.

Empiricism seems like a common-sense way to shut up all these nerdo philosophy/physics kids, but empiricism tends to be the enemy of intelligent discourse these days.